--- a/services/settings/Attachments.sys.mjs
+++ b/services/settings/Attachments.sys.mjs
@@ -144,6 +144,7 @@ export class Downloader {
    * @param {Boolean} [options.fallbackToDump] Use the remote settings dump as a
    *                                         potential source of the attachment.
    *                                         (default: `false`)
+   * @param {string} options.serverUrl
    * @throws {Downloader.DownloadError} if the file could not be fetched.
    * @throws {Downloader.BadContentError} if the downloaded content integrity is not valid.
    * @throws {Downloader.ServerInfoError} if the server response is not valid.
@@ -203,6 +204,7 @@ export class Downloader {
       fallbackToCache = false,
       fallbackToDump = false,
       avoidDownload = false,
+      serverUrl,
     } = options || {};
     if (!attachmentId) {
       // Check for pre-condition. This should not happen, but it is explicitly
@@ -254,6 +256,7 @@ export class Downloader {
         const newBuffer = await this.downloadAsBytes(record, {
           retries,
           checkHash,
+          serverUrl,
         });
         const blob = new Blob([newBuffer]);
         // Store in cache but don't wait for it before returning.
@@ -424,6 +427,7 @@ export class Downloader {
    * @param {Object} options Some download options.
    * @param {Number} options.retries Number of times download should be retried (default: `3`)
    * @param {Boolean} options.checkHash Check content integrity (default: `true`)
+   * @param {String} options.serverUrl
    * @throws {Downloader.DownloadError} if the file could not be fetched.
    * @throws {Downloader.BadContentError} if the downloaded content integrity is not valid.
    * @returns {ArrayBuffer} the file content.
@@ -432,10 +436,11 @@ export class Downloader {
     const {
       attachment: { location, hash, size },
     } = record;
+    const { retries = 3, checkHash = true, serverUrl } = options;
 
-    const remoteFileUrl = (await this._baseAttachmentsURL()) + location;
+    const remoteFileUrl =
+      (await this._baseAttachmentsURL(serverUrl)) + location;
 
-    const { retries = 3, checkHash = true } = options;
     let retried = 0;
     while (true) {
       try {
@@ -484,9 +489,9 @@ export class Downloader {
     await this._rmDirs();
   }
 
-  async _baseAttachmentsURL() {
-    if (!this._cdnURLs[lazy.Utils.SERVER_URL]) {
-      const resp = await lazy.Utils.fetch(`${lazy.Utils.SERVER_URL}/`);
+  async _baseAttachmentsURL(serverUrl = lazy.Utils.SERVER_URL) {
+    if (!this._cdnURLs[serverUrl]) {
+      const resp = await lazy.Utils.fetch(`${serverUrl}/`);
       let serverInfo;
       try {
         serverInfo = await resp.json();
@@ -500,10 +505,9 @@ export class Downloader {
         },
       } = serverInfo;
       // Make sure the URL always has a trailing slash.
-      this._cdnURLs[lazy.Utils.SERVER_URL] =
-        base_url + (base_url.endsWith("/") ? "" : "/");
+      this._cdnURLs[serverUrl] = base_url + (base_url.endsWith("/") ? "" : "/");
     }
-    return this._cdnURLs[lazy.Utils.SERVER_URL];
+    return this._cdnURLs[serverUrl];
   }
 
   async _fetchAttachment(url) {
--- a/services/settings/RemoteSettingsClient.sys.mjs
+++ b/services/settings/RemoteSettingsClient.sys.mjs
@@ -305,6 +305,7 @@ export class RemoteSettingsClient extends EventEmitter {
       localFields = [],
       keepAttachmentsIds = [],
       lastCheckTimePref,
+      serverUrl,
     } = {}
   ) {
     // Remote Settings cannot be used in child processes (no access to disk,
@@ -334,6 +335,7 @@ export class RemoteSettingsClient extends EventEmitter {
     this._lastCheckTimePref = lastCheckTimePref;
     this._verifier = null;
     this._syncRunning = false;
+    this._serverUrl = serverUrl;
 
     // This attribute allows signature verification to be disabled, when running tests
     // or when pulling data from a dev server.
@@ -375,9 +377,12 @@ export class RemoteSettingsClient extends EventEmitter {
   }
 
   httpClient() {
-    const api = new lazy.KintoHttpClient(lazy.Utils.SERVER_URL, {
-      fetchFunc: lazy.Utils.fetch, // Use fetch() wrapper.
-    });
+    const api = new lazy.KintoHttpClient(
+      this._serverUrl || lazy.Utils.SERVER_URL,
+      {
+        fetchFunc: lazy.Utils.fetch, // Use fetch() wrapper.
+      }
+    );
     return api.bucket(this.bucketName).collection(this.collectionName);
   }
 
@@ -604,7 +609,7 @@ export class RemoteSettingsClient extends EventEmitter {
     // We want to know which timestamp we are expected to obtain in order to leverage
     // cache busting. We don't provide ETag because we don't want a 304.
     const { changes } = await lazy.Utils.fetchLatestChanges(
-      lazy.Utils.SERVER_URL,
+      this._serverUrl || lazy.Utils.SERVER_URL,
       {
         filters: {
           collection: this.collectionName,
--- a/toolkit/components/translations/actors/TranslationsParent.sys.mjs
+++ b/toolkit/components/translations/actors/TranslationsParent.sys.mjs
@@ -1034,7 +1034,9 @@ export class TranslationsParent extends JSWindowActorParent {
     }
 
     /** @type {RemoteSettingsClient} */
-    const client = lazy.RemoteSettings("translations-models");
+    const client = lazy.RemoteSettings("translations-models", {
+      serverUrl: "https://firefox.settings.services.mozilla.com/v1",
+    });
     TranslationsParent.#translationModelsRemoteClient = client;
     client.on("sync", TranslationsParent.#handleTranslationsModelsSync);
     return client;
@@ -1420,7 +1422,10 @@ export class TranslationsParent extends JSWindowActorParent {
 
       /** @type {{buffer: ArrayBuffer}} */
       const { buffer } = await client.attachments.download(
-        await TranslationsParent.#bergamotWasmRecord
+        await TranslationsParent.#bergamotWasmRecord,
+        {
+          serverUrl: "https://firefox.settings.services.mozilla.com/v1",
+        }
       );
 
       const duration = Date.now() - start;
@@ -1471,7 +1476,9 @@ export class TranslationsParent extends JSWindowActorParent {
     )) {
       const download = () => {
         lazy.console.log("Downloading record", record.name, record.id);
-        return client.attachments.download(record);
+        return client.attachments.download(record, {
+          serverUrl: "https://firefox.settings.services.mozilla.com/v1",
+        });
       };
       queue.push({ download });
     }
@@ -1495,7 +1502,10 @@ export class TranslationsParent extends JSWindowActorParent {
         onFailure: () => {
           console.error("Failed to download", record.name);
         },
-        download: () => client.attachments.download(record),
+        download: () =>
+          client.attachments.download(record, {
+            serverUrl: "https://firefox.settings.services.mozilla.com/v1",
+          }),
       });
     }
 
@@ -1659,7 +1669,9 @@ export class TranslationsParent extends JSWindowActorParent {
         await chaosMode(1 / 3);
 
         /** @type {{buffer: ArrayBuffer }} */
-        const { buffer } = await client.attachments.download(record);
+        const { buffer } = await client.attachments.download(record, {
+          serverUrl: "https://firefox.settings.services.mozilla.com/v1",
+        });
 
         results[record.fileType] = {
           buffer,