Anecdotally I've never experienced a single one of those bugs in Firefox on Android as a heavy user.

I second this.

Only use ff mobile and never have any issues

I rarely find any of those things. I mean, it does crash, but once every six months, which I don't see as constant.

Hehe, we are on the same boat about not using other browsers. I have been use firefox for the last 18 years, I will continue to do so.

why not Kiwi Browser? uses chromium under the hood. allows chrome extensions to be installed, but most don't work.

Like most small-backing Chromium clones it's usually ~2 months behind on patches (normal and security) and the published source is about ~10 months behind. Being effectively closed for the release version and very small from a development side it does wonky things like redirect your "Google" searches through their servers since they don't have proper search agreements.

I.e. it's basically "an interesting Chromium clone maintained by a couple of folks out of Estonia". If you're cool with that it can be a nifty browser, for many that just makes it to unproven to dump access to their entire online world into.