it'd be really nice to exert pressure on GPay or at least banking apps to add GOS's keys. accepting only Google's keys is anticompetitive.

Most banking apps permit GrapheneOS. We estimate around 10% ban it via the Play Integrity API, which is gradually increasing. The good news is that around a dozen banking apps have added explicit support for GrapheneOS. Swissquote recently implemented it via hardware attestation to check the GrapheneOS verified boot keys per https://grapheneos.org/articles/attestation-compatibility-gu....