Mine’s is the nightly version
LibreWolf
Firefox Focus on mobile with javascript disabled by default for news sites
The one that always ships late with my distro (Fedora) is my favorite, I guess, since it is the one I use :)
For Firefox mobile, it was the Fennec engine where you could easily install any extension… It became a pain with the Fenix engine
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Iceraven on Android; it’s got extensions I use – notably SingleFile — that the main Firefox doesn’t have any more.
The gecko demo that fit on 1 3.5" floppy disk.
Nightly
Firefox containers
Old firefox XUL? When Add-ons isn’t restricted… Well old times… When search toolbar Spyware are everywhere… 😂
Android. It has the extensions I need and is plenty fast as well.