All apps I need for banking, 2 factor authenticator, etc work in my GrapheneOS phone, with the exception of one particular app used for ID authentication in the country I reside. The reason is bc this app uses Google's Play Integrity API to check the phone's OS, and since it does not match with Google's Android OS, it stops working since it does not pass integrity checks. As far as I know, there are few apps that do this, and as time passes more apps are moving towards hardware-attestation tests, as GrapheneOS facilitates, instead of relying Google's Play Integrity.
For me this is not an issue, because the government provides other means for ID authentication, but some other countries only relies on apps, and that might be a show stopper.
My bank app works. Westjet app for flights is very intrusive and needed the special per app compatibility mode turned on to allow app to work. It reduces GrapheneOS exploit prevention for that app, but for some reason Westjet needed more device identity confirmation than my bank app.
I just checked their list, it is different now than when I moved to Graphene, they had support for my Essentials PH1 before. Their support list does have emulated and generic targets, beside pixel targets, but they no longer list the other devices