Hi,
before asking, thanks for all your tutorial you are great.
I would like to suggest a tutorial, something like a third-part tutorial of this : https://www.raywenderlich.com/60998/game-center-tutorial-how-to-make-a-simple-multiplayer-game-with-sprite-kit-part-2
where it is explained how to implement invite friends request and found nearby player to play with. Thanks for listening.