This is a popular thing to say, but is an oversimplification...
Call it anec-data but all my banking apps work in GrapheneOS, and I have several installed. There is one that reduces functionality if SafetyNet fails (have to do the 2fa flow every time I restart the app, can't set as a trusted device and notifications don't work) but it still works to access my account.
That said... I haven't tried to use NFC payments and do carry around a secondary iPhone 15 as my "business phone" these days that pretty much just has payment/banking apps on it, just in case one bank or another decides to suddenly nuke their app on my main phone...