Definitely Florisboard as it has the most features and best theming support but I was using AnySoftKeyboard in the past and it's okay too.

The default built-in GUI Microsoft Store absolutely positively sucks. The winget package manager is also not meant for the regular people.

The next release of FlorisBoard should come soon (hopefully) after the main dev finishes the NLP core implementation. Even if not, I still don't mind using it.

Spell correction works but isn't implemented that well. You need to change the default Android spell checker and then find some raw dictionary of words. But it works in the end.

Can't really recommend Manjaro to new users after the fairly recent controversies.