I use FF on desktop and mobile (although FF on mobile crashes on me, sometimes does not refresh etc.- Android)
I have never had mobile FF crash on me, largely been a good experience.
A few months ago they released a version of Nightly that would crash for most users on startup every time. It was up on the Play store for several days.
That would normally be a buyer-beware situation as with any dev build, but Mozilla had purposely locked several important features - such as about:config configuration and loading any extension - behind the Nightly version, forcing users into that kind of experience.