I use FF on android for a couple months now. Solid browser and sync to desktol and add blocker are nice.
BUT: their page reloading is far too aggressive. You can't buy anything online, since once 2FA is required and you need to open your bank app, confirm, and switch back, the page reloads and the 2FA didn't get through. Tickets and such are the only reason I have still chrome installed.
I haven't been using Firefox for Android because I heard they don't have a WebView Implementation so the firefox browser has to be used beside the Chromium WebView meaning there's an attack surface of two browser engines. I also heard that the Firefox sandboxing and site isolation isn't very good between websites.
I've been using Vanadium WebView and browser because of that.