Gregory's Server
Banning a more secure operating system as part of implementing a fake security feature shows serious anti-security culture at RevolutApp. A company which deliberately permits a device with no patches for 8 years but not a hardened OS does not understand or care about security.
Can see it's clearly because they're banning GrapheneOS because they show an error at login about you using an OS they don't support. It is not a compatibility issue. Meanwhile, they support every insecure OEM fork licensing Google apps no matter how long it hasn't been patched.