Linux should be the focus. Windows Recall is a hell-to-the-no for me, and then having to have 'cloud accounts' to log in on desktops should be demonized. "Oh but you can just run brew for all your .." -- No, no I can't.
FF, being a pioneer of privacy (not anymore, with anonym adds): Go to Settings -> type 'advert', turn that off.
FF, being a major player in FOSS, and community (irc.mozilla.org etc), now I think they do matrix
Many Firefox devs are on Linux; however note that not many Firefox users are on Linux (mostly because desktop Linux has a much much smaller userbase than Windows or Mac). About 4% are Linux, looks like 8-10% Mac, the rest Windows:
https://data.firefox.com/dashboard/hardware
Most Mozilla developers are on Mac, most users are on Windows, so Linux have never been the focus.