If you're looking for a de-Googled #Android phone, I highly recommend GrapheneOS. I switched from using Google Android a few months ago as my daily driver and couldn't be happier.
I don't know about specifically banking applications, but I have to have several apps for work that rely on Google Services, and have had no issues with any of them.
On the note of switching to #linux beware that many distributions are implementing age verification as well through the reliance on systemd.
I have switched to Void Linux from Debian and Fedora, and am so far quite pleased with it. It is certainly a learning process, but I'm very satisfied with the OS.
GrapheneOS (npub1kwa…e0nj)
Void Linux (npub1848…g8za)