With Google Play Services, I've had zero banking app problems.
Tap to pay loss is a drag, but now I just use a card that I carry, anyway.
Discussion
I don't have the option of using a physical card. Neo banking in Canada is a bit of a joke.
The other drawback of GrapheneOS is the camera app has struggled immensely to keep up with stock Android.
I presume it is better now, but when I used GrapheneOS it was horrible. There was a time where you couldn't even take pictures.
It is a tough sell to get people to unlock the bootloader of your $1000 phone only for their phone to half work.
No card. That is extreme.
Regarding GrapheneOS camera, it's not awful, but it's not Google. So I use the Google camera app.