I’ve tried all the Firefox forks I could find, including LibreWolf. It’s not your no-brainer “Non-Mozilla Firefox” you can just switch to. Basic browsing may work, but nothing remotely close to “web-app” will, because they disabled all modern APIs due to privacy concerns.
I'm currently using Iceraven on my Android phone and it's mostly a great experience! It gives access to all sorts of add-ons to block ads, cookies and other internet annoyances, some of which are not yet available on the official FF Android app since Fennec was abandoned. Even if speed were not 100% that of certain mobile browsers (I have not benchmarked them nor noticed any major differences), having no banners show…
I maintain a hardened fork called Mull. I also help maintain Fennec F-Droid. Both are available on F-Droid!
Of extra note, both Iceraven, Mull, and Fennec F-Droid are based on Fenix, not Fennec. Fennec is any Firefox for Android before version 68 and is not secure.