That’s incorrect. When Josh and I did the refactor from UE3 -> UE4 we made sure that it was trivial to support many of them at the same time. It worked in UE3 too, but was much trickier. Now it’s just a matter of requesting the one you want by name, Steam, Facebook, etc. There’s a default that you configure but that isn’t the only one you can have, just the default.
Here’s some code:
Online::GetSubsystem(GetWorld(), NAME_Steam)…
Online::GetSubsystem(GetWorld(), NAME_GameCenter)…