Find a way to ship custom default bookmarks without changing language-packs on macOS
With multi-lingual packages we found that we are changing language packs to customize default bookmarks on macOS (#21879 (closed)).
However, the preference that allowed us to so does not seem to work anymore, and Firefox is showing a lot of warnings.
We should see if we can change the way to customize bookmarks.
I'm not sure if this is just a quirk of the testbuild, but the current state of
about:addons in the multi-locale build is very... warning-y. To add insult to injury, the link behind the buttons all 404 too: