also fennec from f-droid is able to use custom extensions (and also about:config)
it is compiled from firefox stable, with minimal changes, and mozilla telemetry disabled.
https://f-droid.org/en/packages/org.mozilla.fennec_fdroid/
Edit: then I remembered that F-Droid has the quirk of requiring a manual refresh of its repository. I did it and got version 101.1.0 from June 5. Much better.
Your statement is akin to saying: "Firefox on Debian is my solution to Mozilla abandoning FF on desktop"
If FF on Android _were_ abandoned, then so would Fennec.
I use Fennec, but because I know that it the well-supported, actively developed Firefox on Android, but available on F-Droid.
which sadly Mozilla doesn't provide or allow F-Droid maintainers to publish it as "Firefox"