diff --git a/e2e/remote/ansible-collection-versions.spec.ts b/e2e/remote/ansible-collection-versions.spec.ts
new file mode 100644
index 00000000..95b94c24
--- /dev/null
+++ b/e2e/remote/ansible-collection-versions.spec.ts
@@ -0,0 +1,164 @@
+import { type Page, expect, test } from '@playwright/test';
+import { type PulpObject, TestObjects } from '../support/api';
+import { title } from '../support/sign-in';
+import { failureShown, watchPage } from './list-pages';
+
+// The Collection versions tab of an ansible repository and its Add collection
+// dialog work on a plain Pulp server: an empty repository shows the empty state
+// and no error, the dialog lists the collection versions the server holds,
+// adding one puts it in the repository and removing it empties the tab again.
+// The repository is made through the API; the collection version is one the
+// server already holds, which the test never changes.
+
+const COLLECTION_VERSIONS = 'content/ansible/collection_versions/';
+const REPOSITORIES = 'repositories/ansible/ansible/';
+const EMPTY_STATE = 'No collection versions yet';
+
+let objects: TestObjects;
+let repository: PulpObject;
+// A collection version of the server, or undefined when it holds none.
+let collection:
+  { namespace: string; name: string; version: string } | undefined;
+
+test.describe.configure({ mode: 'serial' });
+
+test.beforeAll(async () => {
+  test.setTimeout(180_000);
+  objects = await TestObjects.open('collection-versions');
+  repository = await objects.create(REPOSITORIES, {
+    name: objects.name('repo'),
+  });
+
+  const versions = (await objects.list(COLLECTION_VERSIONS, {
+    fields: 'namespace,name,version',
+  })) as unknown as { namespace: string; name: string; version: string }[];
+  const perCollection = new Map<string, number>();
+  for (const { namespace, name } of versions) {
+    const key = `${namespace}.${name}`;
+    perCollection.set(key, (perCollection.get(key) ?? 0) + 1);
+  }
+  // a collection with few versions keeps the chosen row on the dialog's
+  // first page once the list is filtered by its namespace and name
+  collection = versions.find(
+    ({ namespace, name }) =>
+      (perCollection.get(`${namespace}.${name}`) ?? 0) <= 10,
+  );
+});
+
+test.afterAll(async () => {
+  test.setTimeout(180_000);
+  await objects.cleanUp();
+});
+
+function tabUrl(): string {
+  return `ansible/repositories/detail/${repository.name as string}?tab=collection-versions`;
+}
+
+function label(): string {
+  const { namespace, name, version } = collection as NonNullable<
+    typeof collection
+  >;
+  return `${namespace}.${name} v${version}`;
+}
+
+// The version of the repository the server reports as the latest, by number.
+async function latestVersion(): Promise<number> {
+  const current = await objects.get(repository.pulp_href);
+  return Number(
+    String(current['latest_version_href']).replace(/\/$/, '').split('/').pop(),
+  );
+}
+
+async function openAddDialog(page: Page) {
+  await page.getByRole('button', { name: 'Add collection' }).first().click();
+  const dialog = page.getByRole('dialog');
+  await expect(dialog).toContainText('Select a collection');
+  return dialog;
+}
+
+test('an empty repository shows the empty state, and the Add collection dialog lists the collection versions of the server', async ({
+  page,
+}) => {
+  const watch = watchPage(page);
+
+  await page.goto(tabUrl());
+  await expect(title(page, repository.name as string)).toBeVisible();
+  await expect(page.getByText(EMPTY_STATE)).toBeVisible();
+  await page.waitForLoadState('networkidle');
+  await expect(failureShown(page)).toHaveCount(0);
+  await expect(page.getByText('The stack trace is:')).toHaveCount(0);
+  expect(watch.failed, 'API requests of the tab that failed').toEqual([]);
+
+  const dialog = await openAddDialog(page);
+  await page.waitForLoadState('networkidle');
+  if (collection) {
+    await expect(dialog.getByRole('checkbox').first()).toBeVisible();
+  } else {
+    await expect(dialog.getByText(EMPTY_STATE)).toBeVisible();
+  }
+  await expect(failureShown(page)).toHaveCount(0);
+  await expect(page.getByText('The stack trace is:')).toHaveCount(0);
+  expect(watch.errors, 'uncaught errors of the page').toEqual([]);
+  expect(watch.failed, 'API requests of the dialog that failed').toEqual([]);
+
+  await dialog.getByRole('button', { name: 'Cancel' }).click();
+  await expect(dialog).toHaveCount(0);
+});
+
+test('adding a collection version shows it in the tab and removing it empties the tab again', async ({
+  page,
+}) => {
+  test.skip(!collection, 'the server holds no collection version');
+  test.setTimeout(180_000);
+  const { namespace, name } = collection as NonNullable<typeof collection>;
+  const watch = watchPage(page);
+
+  await page.goto(tabUrl());
+  await expect(page.getByText(EMPTY_STATE)).toBeVisible();
+
+  const dialog = await openAddDialog(page);
+  await dialog.getByRole('textbox', { name: 'namespace' }).fill(namespace);
+  await dialog.getByRole('textbox', { name: 'namespace' }).press('Enter');
+  await dialog.getByRole('button', { name: /Namespace/ }).click();
+  await page.getByRole('menuitem', { name: 'Name', exact: true }).click();
+  await dialog.getByRole('textbox', { name: 'name' }).fill(name);
+  await dialog.getByRole('textbox', { name: 'name' }).press('Enter');
+
+  const row = dialog.getByRole('row').filter({ hasText: label() });
+  await expect(row).toBeVisible();
+  await row.getByRole('checkbox').check();
+  await dialog.getByRole('button', { name: 'Select', exact: true }).click();
+
+  await expect(
+    page.getByText(`Started adding ${label()} to repository`),
+  ).toBeVisible();
+  await expect.poll(latestVersion, { timeout: 60_000 }).toBe(1);
+
+  // the tab lists the content of the version the repository had when the page
+  // loaded, so the page is loaded again to see the new version
+  await page.goto(tabUrl());
+  const added = page.getByRole('row').filter({ hasText: label() });
+  await expect(added).toBeVisible();
+  await expect(page.getByText(EMPTY_STATE)).toHaveCount(0);
+
+  await added.locator('[data-cy=kebab-toggle] button').click();
+  await page.getByRole('menuitem', { name: 'Remove', exact: true }).click();
+  const confirm = page.getByRole('dialog');
+  await expect(confirm).toContainText('Remove collection version?');
+  await confirm.getByRole('button', { name: 'Remove', exact: true }).click();
+
+  await expect(
+    page.getByText(`Removal of ${label()} from repository`),
+  ).toBeVisible();
+  await expect.poll(latestVersion, { timeout: 60_000 }).toBe(2);
+
+  await page.goto(tabUrl());
+  await expect(page.getByText(EMPTY_STATE)).toBeVisible();
+  await expect(page.getByRole('row').filter({ hasText: label() })).toHaveCount(
+    0,
+  );
+
+  await expect(page.getByText('The stack trace is:')).toHaveCount(0);
+  expect(watch.errors, 'uncaught errors of the page').toEqual([]);
+  expect(watch.failed, 'API requests of the tab that failed').toEqual([]);
+});
diff --git a/e2e/remote/list-pages.spec.ts b/e2e/remote/list-pages.spec.ts
index c9eba0db..b532c487 100644
--- a/e2e/remote/list-pages.spec.ts
+++ b/e2e/remote/list-pages.spec.ts
@@ -1,6 +1,8 @@
 import { expect, test } from '@playwright/test';
-import { title } from '../support/sign-in';
 import {
+  absentOptionalPlugin,
+  expectNothingLoaded,
+  expectPageShown,
   failureShown,
   listPages,
   missingExpectedPlugins,
@@ -11,7 +13,11 @@ import {
 
 // Every list page of every installed plugin, and of Pulp core, opens for the
 // admin account with its title, without the error boundary, without an error
-// alert or error state and without an uncaught error in the page.
+// alert or error state and without an uncaught error in the page. A screen
+// this UI does not have shows its placeholder, a route that no longer exists
+// shows the not-found page, and a page of an optional plugin the server does
+// not run says the plugin is not installed; none of them sends a failing
+// request or a request to an endpoint only galaxy_ng serves.
 
 test.beforeAll(async () => {
   if (missingPluginsAllowed()) {
@@ -30,14 +36,16 @@ for (const entry of listPages) {
     // runs anyway: the run reports it the day the page works
     test.fail(!!entry.knownDefect?.admin, entry.knownDefect?.admin ?? '');
 
+    const notInstalled = await absentOptionalPlugin(entry);
     const watch = watchPage(page);
 
     await page.goto(entry.path);
-    await expect(title(page, entry.title)).toBeVisible();
+    await expectPageShown(page, entry, notInstalled);
     await page.waitForLoadState('networkidle');
 
     await expect(page.getByText('The stack trace is:')).toHaveCount(0);
     await expect(failureShown(page)).toHaveCount(0);
     expect(watch.errors, 'uncaught errors of the page').toEqual([]);
+    expectNothingLoaded(watch, entry, notInstalled);
   });
 }
diff --git a/e2e/remote/list-pages.ts b/e2e/remote/list-pages.ts
index 79c78bc1..498870bf 100644
--- a/e2e/remote/list-pages.ts
+++ b/e2e/remote/list-pages.ts
@@ -1,5 +1,6 @@
-import { type Page } from '@playwright/test';
+import { type Page, expect } from '@playwright/test';
 import { apiContext } from '../support/api';
+import { title } from '../support/sign-in';
 
 // Every list page of the application, with the plugin that has to be installed
 // on the server for the page to make sense (null for pages of Pulp core) and
@@ -10,16 +11,27 @@ import { apiContext } from '../support/api';
 // expected to fail with that reason, so it still runs and the run reports it
 // the day the page works. `viewerRefused` marks a page the limited account may
 // not read: the server answers it with 403.
+//
+// `outcome` names a page that is deliberately not a working screen: a
+// placeholder that says the screen is not available yet, or the not-found page
+// of a route that no longer exists. Such a page must show exactly that, with no
+// failed request and no request to an endpoint that only galaxy_ng serves.
+// For these entries `title` is the heading the page shows.
+
+export type Outcome = 'placeholder' | 'not-found';
 
 export interface ListPage {
   name: string;
   path: string;
   plugin: string | null;
   title: string;
+  outcome?: Outcome;
   viewerRefused?: boolean;
   knownDefect?: { admin?: string; viewer?: string };
 }
 
+const NOT_FOUND_TITLE = '404 - Page not found';
+
 export const listPages: ListPage[] = [
   { name: 'Status', path: 'status', plugin: null, title: 'Status' },
   {
@@ -61,12 +73,7 @@ export const listPages: ListPage[] = [
     path: 'search',
     plugin: null,
     title: 'Search',
-    knownDefect: {
-      admin:
-        'The page crashes into the error boundary: it builds a link without the repository name it needs.',
-      viewer:
-        'The page crashes into the error boundary: it builds a link without the repository name it needs.',
-    },
+    outcome: 'placeholder',
   },
   {
     name: 'Ansible repositories',
@@ -85,70 +92,49 @@ export const listPages: ListPage[] = [
     path: 'ansible/collections',
     plugin: 'ansible',
     title: 'Collections',
-    knownDefect: {
-      admin:
-        'The page crashes into the error boundary: it reads the namespace of a collection that the server does not return.',
-    },
+    outcome: 'placeholder',
   },
   {
     name: 'Ansible namespaces',
     path: 'ansible/namespaces',
     plugin: 'ansible',
     title: 'Namespaces',
-    knownDefect: {
-      admin:
-        'The list cannot be loaded: it calls an endpoint that exists only on galaxy_ng and shows a 404 error alert.',
-      viewer:
-        'The list cannot be loaded: it calls an endpoint that exists only on galaxy_ng and shows a 404 error alert.',
-    },
+    outcome: 'placeholder',
   },
   {
     name: 'Ansible my namespaces',
     path: 'ansible/my-namespaces',
     plugin: 'ansible',
-    title: 'Namespaces',
-    knownDefect: {
-      admin:
-        'The list cannot be loaded: it calls an endpoint that exists only on galaxy_ng and shows a 404 error alert.',
-      viewer:
-        'The list cannot be loaded: it calls an endpoint that exists only on galaxy_ng and shows a 404 error alert.',
-    },
+    title: NOT_FOUND_TITLE,
+    outcome: 'not-found',
   },
   {
     name: 'Ansible approvals',
     path: 'ansible/approvals',
     plugin: 'ansible',
-    title: 'Approvals',
-    knownDefect: {
-      admin:
-        'The page is an empty under-construction placeholder with no title.',
-      viewer:
-        'The page is an empty under-construction placeholder with no title.',
-    },
+    title: NOT_FOUND_TITLE,
+    outcome: 'not-found',
   },
   {
     name: 'Ansible imports',
     path: 'ansible/my-imports',
     plugin: 'ansible',
-    title: 'Imports',
-    knownDefect: {
-      admin:
-        'The page loads namespaces from an endpoint that exists only on galaxy_ng and shows a 404 error alert.',
-      viewer:
-        'The page loads namespaces from an endpoint that exists only on galaxy_ng and shows a 404 error alert.',
-    },
+    title: NOT_FOUND_TITLE,
+    outcome: 'not-found',
   },
   {
     name: 'Container repositories',
     path: 'container/containers',
     plugin: 'container',
     title: 'Containers',
+    outcome: 'placeholder',
   },
   {
     name: 'Container remote registries',
     path: 'container/remotes',
     plugin: 'container',
     title: 'Remote registries',
+    outcome: 'placeholder',
   },
   {
     name: 'Deb repositories',
@@ -236,14 +222,17 @@ export async function missingExpectedPlugins(): Promise<string[]> {
   return EXPECTED_PLUGINS.filter((plugin) => !present.has(plugin));
 }
 
-// Skip reason for a page whose plugin the server does not run, or null. The
-// pages of an expected plugin are skipped only when the run allows it; every
-// other plugin (container) is optional.
+// Skip reason for a page whose plugin the server does not run, or null. Only
+// the pages of an expected plugin are skipped, and only when the run allows
+// it. A page of an optional plugin (container) is never skipped: the
+// application says the plugin is not installed, and absentOptionalPlugin names
+// that case.
 export async function missingPlugin(entry: ListPage): Promise<string | null> {
-  if (!entry.plugin) {
-    return null;
-  }
-  if (EXPECTED_PLUGINS.includes(entry.plugin) && !missingPluginsAllowed()) {
+  if (
+    !entry.plugin ||
+    !EXPECTED_PLUGINS.includes(entry.plugin) ||
+    !missingPluginsAllowed()
+  ) {
     return null;
   }
   return (await installedPlugins()).has(entry.plugin)
@@ -251,16 +240,35 @@ export async function missingPlugin(entry: ListPage): Promise<string | null> {
     : `the ${entry.plugin} plugin is not installed on this server`;
 }
 
-// What a page did while it loaded: uncaught errors, and the answers of the
-// API that were errors.
+// The plugin of a page when that plugin is optional and the server does not
+// report it, otherwise null. The page then shows the not-installed page in
+// place of its screen.
+export async function absentOptionalPlugin(
+  entry: ListPage,
+): Promise<string | null> {
+  if (!entry.plugin || EXPECTED_PLUGINS.includes(entry.plugin)) {
+    return null;
+  }
+  return (await installedPlugins()).has(entry.plugin) ? null : entry.plugin;
+}
+
+// What a page did while it loaded: uncaught errors, the paths of the API
+// requests it sent, and the answers of the API that were errors.
 export interface PageWatch {
   errors: string[];
+  requests: string[];
   failed: { url: string; status: number }[];
 }
 
 export function watchPage(page: Page): PageWatch {
-  const watch: PageWatch = { errors: [], failed: [] };
+  const watch: PageWatch = { errors: [], requests: [], failed: [] };
   page.on('pageerror', (error) => watch.errors.push(error.message));
+  page.on('request', (request) => {
+    const { pathname } = new URL(request.url());
+    if (pathname.startsWith('/pulp/api/')) {
+      watch.requests.push(pathname);
+    }
+  });
   page.on('response', (response) => {
     const { pathname } = new URL(response.url());
     if (pathname.startsWith('/pulp/api/') && response.status() >= 400) {
@@ -277,3 +285,51 @@ export function failureShown(page: Page) {
     .locator('.pf-v5-c-alert.pf-m-danger')
     .or(page.getByRole('button', { name: 'Retry', exact: true }));
 }
+
+// A request path that only a galaxy_ng server answers: its internal UI API,
+// or its collection API, which is a second v3/ below the API root.
+export function galaxyOnly(pathname: string): boolean {
+  return /\/_ui\//.test(pathname) || pathname.startsWith('/pulp/api/v3/v3/');
+}
+
+// The page of an entry is on screen: the not-installed page when the plugin
+// is optional and absent, otherwise the entry's title, and for a placeholder
+// its sentence.
+export async function expectPageShown(
+  page: Page,
+  entry: ListPage,
+  notInstalled: string | null,
+): Promise<void> {
+  if (notInstalled) {
+    await expect(title(page, 'Plugin not installed')).toBeVisible();
+    await expect(
+      page.getByText(
+        `The ${notInstalled} plugin is not installed on this Pulp server.`,
+      ),
+    ).toBeVisible();
+    return;
+  }
+  await expect(title(page, entry.title)).toBeVisible();
+  if (entry.outcome === 'placeholder') {
+    await expect(
+      page.getByText('This screen is not available in this UI yet.'),
+    ).toBeVisible();
+  }
+}
+
+// A placeholder, a not-found page and a not-installed page load nothing of
+// their own: no failed answer, and no request to a galaxy-only endpoint.
+export function expectNothingLoaded(
+  watch: PageWatch,
+  entry: ListPage,
+  notInstalled: string | null,
+): void {
+  if (!entry.outcome && !notInstalled) {
+    return;
+  }
+  expect(watch.failed, 'API requests of the page that failed').toEqual([]);
+  expect(
+    watch.requests.filter(galaxyOnly),
+    'requests of the page to endpoints only galaxy_ng serves',
+  ).toEqual([]);
+}
diff --git a/e2e/remote/list-pages.viewer.spec.ts b/e2e/remote/list-pages.viewer.spec.ts
index 6eea18b2..ce1fcef3 100644
--- a/e2e/remote/list-pages.viewer.spec.ts
+++ b/e2e/remote/list-pages.viewer.spec.ts
@@ -1,6 +1,9 @@
 import { expect, test } from '@playwright/test';
 import { title } from '../support/sign-in';
 import {
+  absentOptionalPlugin,
+  expectNothingLoaded,
+  expectPageShown,
   failureShown,
   listPages,
   missingPlugin,
@@ -12,6 +15,8 @@ import {
 // is refused by the server with 403; it may show the title, or say so with an
 // error, but an error of any other kind (404, 500, no answer) is a fault of
 // the page. Neither may ever meet the error boundary or an uncaught error.
+// A placeholder, a not-found page and a not-installed page are shown to this
+// account exactly as to the admin.
 
 for (const entry of listPages) {
   const how = entry.viewerRefused
@@ -22,6 +27,7 @@ for (const entry of listPages) {
     test.skip(absent !== null, absent ?? '');
     test.fail(!!entry.knownDefect?.viewer, entry.knownDefect?.viewer ?? '');
 
+    const notInstalled = await absentOptionalPlugin(entry);
     const watch = watchPage(page);
 
     await page.goto(entry.path);
@@ -30,7 +36,7 @@ for (const entry of listPages) {
         title(page, entry.title).or(failureShown(page)).first(),
       ).toBeVisible();
     } else {
-      await expect(title(page, entry.title)).toBeVisible();
+      await expectPageShown(page, entry, notInstalled);
     }
     await page.waitForLoadState('networkidle');
 
@@ -40,6 +46,7 @@ for (const entry of listPages) {
     if (!entry.viewerRefused) {
       await expect(failureShown(page)).toHaveCount(0);
       expect(watch.failed, 'API requests of the page that failed').toEqual([]);
+      expectNothingLoaded(watch, entry, notInstalled);
       return;
     }
 
diff --git a/e2e/support/api.ts b/e2e/support/api.ts
index 2503036f..645f2bd9 100644
--- a/e2e/support/api.ts
+++ b/e2e/support/api.ts
@@ -72,6 +72,7 @@ const REPOSITORIES = [
   'repositories/deb/apt/',
   'repositories/rpm/rpm/',
   'repositories/python/python/',
+  'repositories/ansible/ansible/',
 ];
 const REMOTES = [
   'remotes/file/file/',