I've got the same issue on grapheneos Android 13 with the dkb tan2go app like @RubixCube .
The normal DKB banking apps work fine without google play (no notifications though).
The tan2go app freezes at the dkb logo in the main user profile without g services, in work profile with g services and in another user profile with g services.
enabling "exploit protection compatibility mode" does not work. Neither DISABLE_HAHRDENED_MALLOC or ENABLE_COMPAT_VA_39_BIT.
MetropleX do you have another idea how to solve the issue?