I found a lengthy discussion for this exact issue raised in GrapheneOS community in this thread: Revolut mobile finance - not supported on devices with custom firmware problem - GrapheneOS Discussion Forum
TLDR: Indeed, Revolut started blocking custom ROMs.
A possible fix (confirmed by me) is to install previous version of the app (10.54 or 1005403809) and log in with it, after which the app may be updated (as of 3 Dec 2024). This may be done by “Manual download” in the Aurora store by providing 1005403809 version number.