The GrapheneOS community maintains a list of banking apps compatibility. In a nutshell, most banking apps that haven't been infected by Play Integrity work just fine.I have yet to find a US app that does not work, but some European banking apps no longer do. If switching banks isn't an option, my suggestion is to keep an old or cheap "certified" phone for that purpose. Most of us have old hardware lying around so that is a fairly natural solution. Note that flashing the OS on a Pixel is reversible, so one option is to go back to the stock OS after upgrading to a newer model.

I have found websites for accessing my banking to be pretty great. Do we really need banking apps?