Most DRM / banking apps work fine for me through the browser and you can add them to your home screen. Android / Samsung Pay will stop working, but if you have a Garmin watch, you can still pay with that.
Big thank you to the GrapheneOS team! I have been running it for a week now on my 9pro and the user / app sandboxing is great. If there's a way to donate with cryptocurrency or help contribute, let me know!