Comment by grapheneos

Banking app compatibility has greatly improved, mainly due to GrapheneOS working around bugs in the apps and adding per-app opt-out for exploit protections known to cause incompatibilities. Around a dozen banking apps have explicitly permitted using GrapheneOS in one way or another. Some removed or changed checks they had to begin permitting it. Other apps began verifying it and potentially other operating systems via Android hardware attestation as an alternative to the Play Integrity API.

There are around 6-8 banking companies which have made changes to explicitly permit GrapheneOS that we're aware of and several have multiple apps which add up to around a dozen apps. There are likely other apps which have made changes to support it without us being aware. Compatibility has improved a lot and we can't attribute that all to any one particular change.