It’s so unfortunate that Firefox on Android, for some reason, never worked well with password managers (as I understand it, it doesn’t support the APIs that Android has for them). Sometimes it’ll trigger the manager, more often, it won’t. Infuriating and a deal breaker for me.
I’ll give it another go, maybe this has been improved recently.
Edit gave it another crack, gosh, it actually works now!
The absolute memest.