de0u Have you red this? It seems a official answer by GrapheneOS...
We're going to be adding a toggle for blocking the Play Integrity API in a way that acts as if the service is currently down. We've found that many apps do not correctly use it and still allow using the app if it's unavailable because their service only has soft enforcement of the Play Integrity API. It's possible this will be enough to get Revolut working but we don't know at this point. They're going out of the way to try banning using alternate OSes and can upgrade that over time.