Comment by IlikeKitties

The answer is it depends. Banking and similar Apps trying to "protect" the user from themselves aka treat the user like a retarded child do this through several mechanisms:

> Google Play Integrity

Essentially a Google API that App Developers integrate that checks if the device runs an Operating System signed by Google as "Play Certified". This can go as far as being backed by a hardware trusted platform module. I doubt Google will certify GrapheneOS given their modifications towards sandboxing the play services. This can be faked to a degree but GrapheneOS choses not to do it and to fake the TPM part you need leaked keys. For more details on how to fake it look at this thread: https://xdaforums.com/t/guide-how-to-pass-strong-integrity-o...

> Fingerprinting the Device OS

This can very from app to app and just tries to fingerprint the device in many ways to see if it's running a custom rom of some kind. This does things like check to see if the bootloader is unlocked or if root is installed. I think this is something an official grapheneos phone might fix since the phone vendor could allow grapheneos to sign their releases as native equivalent

> Banning GrapheneOS by Name

Some Apps Developers literally ban GrapheneOS by name.

> Failures due to Google Play Sandboxing

Since GrapheneOS sandboxes Google Play Services there might be compatibility issues that prevent the app from working right. This would likely be unaffected by a GrapheneOS Phone.

> Failures due to Advanced Security Features

Some Apps just don't "like" the advanced security features like the hardened malloc and other protections and just fail. This can be disabled most of the time