Curve works on GrapheneOS but requires sandboxed Google Play. There are European banking apps with support for tap-to-pay without Google Play. If you're not in Germany, the only way to do without sandboxed Google Play is getting an account at one of those banks. We don't have a specific list of those banks on hand.
Ah ok fair, if your GrapheneOS isn't running the sandboxed google play services, not even in a separate profile, then I don't know if it works.
I have failed to get Curve running after installing GrapheneOS on a new device.
It requires sandboxed Google Play. If you want to avoid that, you need an account at one of the European banks with tap-to-pay not using Google Pay and an app which can run without Google Play. We don't have a specific list but there are a bunch throughout Europe.