Looking for logging into the Play Services Serverside site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Play Services Serverside site. After that you can login as usual with your login credentials.
https://developers.google.com/games/services/android/signin
https://developers.google.com/games/services/android/offline-access
https://developers.google.com/identity/sign-in/web/server-side-flow
https://stackoverflow.com/questions/38649041/set-up-google-play-games-services-clientserver
https://forum.unity.com/threads/please-help-client-server-authentication-for-google-play-services.249197/
https://android-developers.googleblog.com/2013/01/verifying-back-end-calls-from-android.html
https://www.youtube.com/watch?v=ykSFAs6S_Kg
https://gist.github.com/ianbarber/5170508
https://docs.gamesparks.com/tutorials/social-authentication-and-player-profile/google--authentication.html
https://www.npmjs.com/package/react-native-google-signin
http://www.evanlin.com/server-side-iap-verification-google-play/
https://android.jlelse.eu/everything-you-need-to-know-about-google-plays-in-app-billing-29b728a32822
https://firebase.google.com/docs/auth/admin/