I have what looks like a solution using SteamSockets.
Enable the SteamSockets plugin, and use these settings in your DefaultEngine.ini:
[/Script/Engine.GameEngine]
!NetDriverDefinitions=ClearArray
+NetDriverDefinitions=(DefName=“GameNetDriver”,DriverClassName=“/Script/SteamSockets.SteamSocketsNetDriver”,DriverClassNameFallback=“/Script/OnlineSubsystemUtils.IpNetDriver”)[OnlineSubsystem]
DefaultPlatformService=Steam[OnlineSubsystemSteam]
bEnabled=true
SteamDevAppId=480
Replace 480 with your SteamDevAppId if you have one.
You can also add:
[PacketHandlerComponents]
+Components=OnlineSubsystemSteam.SteamAuthComponentModuleInterface
for dedicated servers (or P2P, but less necessary for good auth).
I’ve only done some quick testing, some local dev builds on 2 PCs on the same LAN works ok, as does uploading to Steamworks and installing via steam. I can host a session, it comes up in the search (with ping in ms), join the session, and once in play the game, I don’t have any other features around steam or sessions implemented, but the basics seem ok.
I’ll dig into the logs to see if there is anything funky going on, but I’ve run out of time for now, GL!