Hello @MB,
It would be great if you would consider creating a new "Sign in with Apple" authentication premium plugin that doesn't rely on third-party services.
The popular top 3 authentication services are Google, Facebook and Apple with the latter being the most privacy-focused and least intrusive with the information shared.
I'm pretty sure there will be demand for it as is the case with any premium plugin that provides a value-added service that does not rely on third-party services or subscriptions.
Thank you.
Wiz