EARTH DEFENSE FORCE 6 - About sign in with an Epic Games account. - Steam News
For this game, to enhance cross play and online functionality, Online play requires signing in to your Epic Games account. We apologize for the lack of advance notice. Signing in to your Epic Games account is required the first time you play online. Usuall...
Any multiplayer game should offer LAN-based P2P and/or self-hosted server options as far as I'm concerned, just because that's totally future proof. That should just be a default feature for a multiplayer game.
Beyond that you have to pick something, because normies aren't going to run their own servers and using open P2P via the internet is all kinds of security holes.
I do wonder what they were using before, Steamworks I assume? There's nothing wrong with that, but it only works on Steam.
I think its just p2p which should still be the case in edf 6 unless you are using crossplay.