Hello!
I solved it by adding SteamSockets plugin and dependency.
Then i just updated my DefaultEngine.ini
[/Script/Engine.GameEngine]
!NetDriverDefinitions=ClearArray
+NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="/Script/SteamSockets.SteamSocketsNetDriver",DriverClassNameFallback="/Script/SteamSockets.SteamNetSocketsNetDriver")
[OnlineSubsystem]
DefaultPlatformService=Steam
[OnlineSubsystemSteam]
bEnabled=true
SteamDevAppId=480
bInitServerOnClient=true
[/Script/OnlineSubsystemSteam.SteamNetDriver]
NetConnectionClassName="OnlineSubsystemSteam.SteamNetConnection"
Notice the actual netDriverDefinitions.