[firebase_auth] How to get user email for sign-in with Apple

[ghost]

I am trying debug a Flutter app which uses Firebase Authentication with Apple as sign-in provider and I am struggling to configure it correctly such that I can receive the user email property.

When a user signs-un with Apple in most cases Firebase (implemented as in the Firebase guide) is not registering the email or any type of identifier is shown in Firebase Authentication. In some cases the identifier is an email using the privaterelay.appleid.com domain, but it is rare.

In addition, the UserCredential.user object does not have any properties (all are null).

This works perfectly with Google and Email-password, and a few months ago it was also working for Apple but it has stopped working. (without the need to use 3rd party packages such as sign_in_with_apple)