Have your app successfully received approval from Apple and been launched?
Because I am facing the same problem.
EntryPointNotFoundException: GKLocalPlayer_GetLocal assembly: type: member:(null)
I can not log in to game center in the editor of Unity or simulator of xcode.
Otherwise there is no problem at all on real device.
Thus I uploaded to app store connect and ger rejected.
Please let me know how you solve this problem. Thanks!