I posted this in their forum:
I was checking if any Firefox forks are usable on flx1. LibreWolf don't start because GPU missing error, zen bowser works, but not very adaptive and left side bar takes too much space. Waterfox don't have arm64 builds. Finally floorp seems to work OK, it is mostly adaptive for browsing, settings not much, but you can scroll and adjust. If we scale to fit in mobile settings, a small right panel is lost but seems good. There is no immediate reason to switch since Mozilla tos don't apply, but good to support forks to keep Mozilla under pressure. The outcry helped them backtrack a bit. So if you are looking for forks, floorp is the only option right now.
This was the reply I got,
Barry (Bardia San): you can check with librewolf on what build flag they disabled that makes their browser not work with gles and if they fix that it will work
Since Firefox, zen browser and floorp works, it should be possible to run librewolf also.
Currently firefox-mobile-config only supports librewolf among forks. So would be good if flx1 users can easily switch to librewolf.