My bank does let me use such a device. In fact all big banks I use (and I use about a half dozen) work just fine on GrapheneOS.
> If I want to participate it modern life, where I live, I need an Android (Google blessed) or Apple device.
"Modern life..." - wow. The only thing I'm not doing that you are is tap to pay with your phone. I have cards that work just fine for this use case. Stone age, right? Not sure if anyone could survive in a modern society without it. o_O
Tbf banks are truly driving the coercion. My banks used to have functional apps on bare GrapheneOS, but nowadays they won't launch without Play Services (to wich I can deny network access, pretty neat of GrapheneOS). Plus my main bank now requires the app even for web access. Nightmarish.