So, I installed 3 bank apps, 2 from the same bank. And the conclusion is....... (hard to do a drumroll on a forum): GrapheneOS is bloody awesome !!
All 3 apps installed withouth any issues whatsoever. They aren't on the community-kep list so I will try to find a way to add them or tell inform someone who can. I felt a little bit stupid to have been so "nervous" about installing them (I am no tecchie) as it was super straight forward.
So therefore, next are my donations to Graphene and Side of burritos.