https://wccftech.com/epic-games-users-wont-be-able-to-use-sign-in-with-apple-from-september-11/

As per a new tweet posted by Epic Games' account, users will not be able to use "Sign in with Apple" functionality on any platform after September 11, 2020. To ensure that accounts continue to be accessible, the company is advising users to update their profiles with their actual email address.

"Sign in with Apple" is an authentication mechanism by the company that aims to provide a secure method of signing in to apps and games, without having their private information like email address, be shared with everyone. Compared to services like Google and Facebook, using "Sign in with Apple" means that users are not tracked on any website or app where they use this service.