Did a bit of research and found out the feature is available on Fennec F-Droid too via about:config.

Here’s how to enable: https://community.mozilla.org/en/campaigns/firefox-cookie-banner-handling/

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!

I use firefox clear and it doesn’t even haven cocky support.(longer than one session)