https://github.com/mozilla/addons/issues/708
https://github.com/mozilla/addons-frontend/issues/4610

diff --git browser/app/profile/firefox.js browser/app/profile/firefox.js
index 621900f90fc1..401ef9074bd0 100644
--- browser/app/profile/firefox.js
+++ browser/app/profile/firefox.js
@@ -38,7 +38,7 @@ pref("extensions.postDownloadThirdPartyPrompt", true);
 // Preferences for AMO integration
 pref("extensions.getAddons.cache.enabled", true);
 pref("extensions.getAddons.get.url", "https://services.addons.mozilla.org/api/v4/addons/search/?guid=%IDS%&lang=%LOCALE%");
-pref("extensions.getAddons.search.browseURL", "https://addons.mozilla.org/%LOCALE%/firefox/search?q=%TERMS%&platform=%OS%&appver=%VERSION%");
+pref("extensions.getAddons.search.browseURL", "https://addons.mozilla.org/%LOCALE%/firefox/search?q=%TERMS%&platform=Linux&appver=%VERSION%");
 pref("extensions.getAddons.link.url", "https://addons.mozilla.org/%LOCALE%/firefox/");
 pref("extensions.getAddons.langpacks.url", "https://services.addons.mozilla.org/api/v4/addons/language-tools/?app=firefox&type=language&appversion=%VERSION%");
 pref("extensions.getAddons.discovery.api_url", "https://services.addons.mozilla.org/api/v4/discovery/?lang=%LOCALE%&edition=%DISTRIBUTION%");
@@ -204,8 +204,8 @@ pref("app.update.langpack.enabled", true);
 //  .. etc ..
 //
 pref("extensions.update.enabled", true);
-pref("extensions.update.url", "https://versioncheck.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=%APP_OS%&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE%");
-pref("extensions.update.background.url", "https://versioncheck-bg.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=%APP_OS%&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE%");
+pref("extensions.update.url", "https://versioncheck.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=Linux&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE%");
+pref("extensions.update.background.url", "https://versioncheck-bg.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=Linux&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE%");
 pref("extensions.update.interval", 86400);  // Check for updates to Extensions and
                                             // Themes every day
 
diff --git toolkit/mozapps/extensions/internal/AddonRepository.sys.mjs toolkit/mozapps/extensions/internal/AddonRepository.sys.mjs
index f906f244b658..7bb2eb6697c6 100644
--- toolkit/mozapps/extensions/internal/AddonRepository.sys.mjs
+++ toolkit/mozapps/extensions/internal/AddonRepository.sys.mjs
@@ -596,7 +596,7 @@ export var AddonRepository = {
       addon.version = String(aEntry.current_version.version);
       if (Array.isArray(aEntry.current_version.files)) {
         for (let file of aEntry.current_version.files) {
-          if (file.platform == "all" || file.platform == lazy.PLATFORM) {
+          if (file.platform == "all" || file.platform == "linux" || file.platform == lazy.PLATFORM) {
             if (file.url) {
               addon.sourceURI = lazy.NetUtil.newURI(file.url);
             }
diff --git toolkit/mozapps/extensions/internal/XPIDatabase.jsm toolkit/mozapps/extensions/internal/XPIDatabase.jsm
index 03186dad43a4..4053fc6f2702 100644
--- toolkit/mozapps/extensions/internal/XPIDatabase.jsm
+++ toolkit/mozapps/extensions/internal/XPIDatabase.jsm
@@ -634,7 +634,7 @@ class AddonInternal {
     // Something is causing errors in here
     try {
       for (let platform of this.targetPlatforms) {
-        if (platform.os == Services.appinfo.OS) {
+        if (platform.os == "Linux" || platform.os == Services.appinfo.OS) {
           if (platform.abi) {
             needsABI = true;
             if (platform.abi === abi) {