Also PUBG, which runs on UE4, uses AWS (and Azure) for their dedicated servers.. I wonder if they're on GameLift for the AWS ones or if they rolled their own setup..

Those engines do come with some networking I believe, but I don't think they come with full server-side game code libraries for matchmaking, server routing, etc..

But maybe I'm wrong, I've only dabbled with those engines as a hobbyist.