Add NC Account with "User Account creation" policy disabled

### Is your feature request related to a problem? Please describe.
We're running Android with a mobile device management. Account creation is disabled since we don't want our users to create Google Accounts etc.
When opening the Nextcloud App I'll simply get "Forbidden by Admin" (the Device Administrator Dialog on Android) and the App will crash.
Android 11 with NC 3.20.1

### Describe the solution you'd like
We would like the NC app to behave like Davx5 for example.I'm not aware of the technical background, but for some reason I can add DAV Accounts in Davx5 with the "Disable adding new users and profiles" policy enabled.
Both Apps are pre-installed by default, so there should not be a difference in the settings...

### Describe alternatives you've considered
Allowing Account creation by the user. This is not viable for us. E.g. the Google Calendar App will ask for an Google Account.

### Additional context
Screenshot of the error