Firefox has never put a priority on privacy. Just take a glance at their privacy policy. And it's plain to see that they are moving further away from it every day.
There are a dozen Firefox forks though. Mulch, DDG, TOR, Fennic, Bromite, etc.
There was the time when Daniel Micay was the project lead and I wouldn't trust him either.
The current leadership seems fine though. I dislike that they only want to support Pixel phones but other than that I don't see any issues.
Functional like mull? Oh wait. It has been shut down.
If it works, it works. Havent had any problem with firefox. So i stick with it. I dont have time pondering what browser to use every single time stuff like this happens.
I use Iceraven currently. It's a Firefox fork. Back when I started to use it, It was one of only two browsers (other being Smart Cookie Web Preview) to support extension sideloading on Android.
I don't think Iceraven is as hardened as Mull, but it is updated on a regular basis. Either case, for most folks, regular Firefox should do the trick. There is also Waterfox, another FF fork on desktop/mobile but it hardly has much to distinguish itself.
Currently I'm using Chromite (added some more blocklists),
Fennac (hardened as much as I can),
and Brave ( I known I known. I only use it when some website just don't work)