You can override AGameModeBase::InitNewPlayer and pass in the FName of your PlayerStart as the Portal parameter. InitNewPlayer calls FindPlayerStart, which searches through the PlayerStart objects for one that matches your name.
You can override AGameModeBase::InitNewPlayer and pass in the FName of your PlayerStart as the Portal parameter. InitNewPlayer calls FindPlayerStart, which searches through the PlayerStart objects for one that matches your name.