Upstream builds only include devtools in English and Chinese. But there are more translations available in the source.

--- src/build/config/locales.gni.orig
+++ src/build/config/locales.gni
@@ -169,9 +169,8 @@ platform_pak_locales = all_chrome_locale
 if (is_android) {
   platform_pak_locales -= _non_android_locales
   extended_locales -= _non_android_locales
-} else {
-  platform_pak_locales -= extended_locales
 }
+extended_locales = []
 
 # The base list for all platforms except Android excludes the extended locales.
 # Add or subtract platform specific locales below.
--- src/chrome/app/resources/locale_settings_linux.grd.orig
+++ src/chrome/app/resources/locale_settings_linux.grd
@@ -4,7 +4,6 @@
     <output filename="grit/platform_locale_settings.h" type="rc_header">
       <emit emit_type='prepend'></emit>
     </output>
-    <if expr="is_android">
       <output filename="platform_locale_settings_as.pak" type="data_package" lang="as" />
       <output filename="platform_locale_settings_az.pak" type="data_package" lang="az" />
       <output filename="platform_locale_settings_be.pak" type="data_package" lang="be" />
@@ -31,7 +30,6 @@
       <output filename="platform_locale_settings_uz.pak" type="data_package" lang="uz" />
       <output filename="platform_locale_settings_zh-HK.pak" type="data_package" lang="zh-HK" />
       <output filename="platform_locale_settings_zu.pak" type="data_package" lang="zu" />
-    </if>
     <output filename="platform_locale_settings_af.pak" type="data_package" lang="af" />
     <output filename="platform_locale_settings_am.pak" type="data_package" lang="am" />
     <output filename="platform_locale_settings_ar.pak" type="data_package" lang="ar" />
@@ -39,6 +37,7 @@
     <output filename="platform_locale_settings_bn.pak" type="data_package" lang="bn" />
     <output filename="platform_locale_settings_ca.pak" type="data_package" lang="ca" />
     <output filename="platform_locale_settings_cs.pak" type="data_package" lang="cs" />
+    <output filename="platform_locale_settings_cy.pak" type="data_package" lang="cy" />
     <output filename="platform_locale_settings_da.pak" type="data_package" lang="da" />
     <output filename="platform_locale_settings_de.pak" type="data_package" lang="de" />
     <output filename="platform_locale_settings_el.pak" type="data_package" lang="el" />
--- src/third_party/devtools-frontend/src/config/gni/devtools_grd_files.gni.orig
+++ src/third_party/devtools-frontend/src/config/gni/devtools_grd_files.gni
@@ -2,6 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/devtools.gni")
+import("//$devtools_root_location/config/gni/i18n.gni")
+
 # This represents all the files expected to be be in the GRD. The file
 # has two lists, one for files expected for the Release build
 # (is_debug=false), and another for the Debug build (is_debug=true).
@@ -648,6 +651,15 @@ grd_files_release_sources = [
   "front_end/worker_app.html",
 ]
 
+
+grd_files_release_sources -= [
+    "front_end/core/i18n/locales/en-US.json",
+    "front_end/core/i18n/locales/zh.json"
+]
+foreach(locale, bundled_devtools_locales) {
+    grd_files_release_sources += [ "front_end/core/i18n/locales/$locale.json" ]
+}
+
 grd_files_debug_sources = [
   "front_end/core/common/App.js",
   "front_end/core/common/AppProvider.js",
--- src/third_party/devtools-frontend/src/config/gni/i18n.gni.orig
+++ src/third_party/devtools-frontend/src/config/gni/i18n.gni
@@ -5,6 +5,9 @@
 import("//build/config/devtools.gni")
 
 remote_devtools_locales = [
+]
+
+bundled_devtools_locales = [
   "af",
   "am",
   "ar",
@@ -85,9 +88,6 @@ remote_devtools_locales = [
   "zh-HK",
   "zh-TW",
   "zu",
-]
-
-bundled_devtools_locales = [
   "en-US",
   "zh",
 ]