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 :)
Iceraven on Android; it's got extensions I use -- notably SingleFile
that the main Firefox doesn't have any more.
Old firefox XUL? When Add-ons isn't restricted.. Well old times.. When search toolbar Spyware are everywhere.. ๐
Nightly
Firefox containers
For Firefox mobile, it was the Fennec engine where you could easily install any extension... It became a pain with the Fenix engine
The gecko demo that fit on 1 3.5" floppy disk.
Android. It has the extensions I need and is plenty fast as well.
Firefox
A place to discuss the news and latest developments on the open-source browser Firefox