

idk, maybe the app wants to check if it runs on normal phone hardware, not some reverse engineering virtualization? Or something like: if the OS is verified and unrooted, no secrets get out?
Funny thing is I can use banking grapheneOS phone and the main Health insurance app, but not the Health Insurance TeleDoc-App. Personally I think apps that need GSM or at least be officially google boot verified are apps made by lazy morons, but that’s just a guess.
Apps check if Google says this device is stock and original. Booting alternative OSes is allowed but frowned upon. And of course doesn’t get a Google approval signature. Something like that. Basically programmers not wanting to make the checking themselves and relying on Google to tell them what devices are “secure”.