@timconsidine the game changer actually seems to be the possibility to install the regular Play Services with Play Store in Grapheneos. i could not see any disadvantages to this yet, so far i could use all apps. About the functionality of the sandbox I could only repeat what Daniel Micay writes on his website. Daniel has also built a bypass function for the location requests by Google services. These are routed through the OS and served from there. Google gets very little of this and the apps get their "fake" location info.
I use the banking apps from DKB, ING, Lbb-Berlin (Amazon Prime VISA), N26 and PayPal. Everything works.
I used to be a hard iPhone and Mac user, but switched from iOS completely to AOSP with GrapheneOS and I'm waiting for a Linux notebook with a good processor that can replace Apple's M1.
Would you like me to test an app for you? Of course, only the start of the app and the general functions?