Questions

I found this info in the official doc:

"For users to authenticate with your web service, you must have an existing app in the App Store that uses Sign in with Apple."

It is kind of chicken-and-egg problem. Is it possible to get it work? Maybe I need to deploy my app without Sign in with Apple feature and after that enable it?

Apple's Doc:

https://developer.apple.com/documentation/sign_in_with_apple/configuring_your_environment_for_sign_in_with_apple#3743335