GrapheneOS I really was hoping for another feedback from you, because that issue almost definitely is not connected to Play Integrity, because otherwise the Revolut apps would not run on plain vanilla crDroid without GAPPS/microG.
The catch is, this issue really is a show-stopper for a lot of people (including myself and my whole family), because Revolut can just not be replaced by any other service, as it's more than just a personal banking app, but also investing, for business and a crypto currency exchange (hence three different apps: Revolut, Revolut Business and Revolut X; all three causing the same issue).