This is a Firefox Android fork with some interesting features.
You can sideload XPIs which means you can use any extensions you want, whether they really work on Android or not. uMatrix mostly works for example. You can show extensions in the nav bar, so you can see that uBlock Origin is blocking 8 elements on that page etc.
The development seems to go in fits and starts for this.
Sideloading xpi’s is possible on Iceraven as well. I used Smart Cookie Web preview in the past but it was slightly lighter in terms of feature set then.