The problem is we disabled the feature that users can consent to 3rd party apps
UsersPermissionToUserConsentToAppEnabled : False
I managed to give admin consent for iOS Accounts, so problem solved until the client-id changes. I couldn't find much info on this issue and also MS support couldn't help. Is it so special that we disabled user consent in our tenant?
There is no issue here, the folks at Apple simply updated the app to use Modern authentication, finally. It's actually a good thing as it means you can have "native" MFA experience and so on. The consent is also part of this, and you already know how to control it, which is another good thing - you have a better understanding which users are using which apps, etc. You are certainly not the first organization to disable that option :)
Best Response confirmed by
Ruth de Groot (Occasional Contributor)