Monero_lover
I used to use GBoard as well and also have to switch back and forth between several languages. When I made the move to GrapheneOS, I gave the standard keyboard a chance.
With a long press on the space bar you can quickly access the languages which you can activate beforehand under settings>system>keyboard>on-screen-keyboard>keyboard>languages.
Dictionaries for the spell checker are also pre-installed for the languages you mentioned.
I got used to the keyboard within a few days and -even if typing takes a little longer (swiping doesn't work)- I don't miss GBoard at all.