Just FYI, as of UE 5.6 OnlineSubsystemSteam.SteamNetDriver and OnlineSubsystemSteam.SteamNetConnection has been deprecated in favor of SteamSockets. So currently you are not using Steam for networking, just the base IP net driver. You can find more info here. Is there anyone who can run the Online Subsystem Steam properly in UE 5.6?
Make sure to enable the SteamSockets plugin and use the following config settings:
; The net drivers to be used by the game.
[/Script/Engine.GameEngine]
!NetDriverDefinitions=ClearArray
+NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="/Script/SteamSockets.SteamSocketsNetDriver",DriverClassNameFallback="/Script/OnlineSubsystemUtils.IpNetDriver")
; Specific configuration of the Steam Sockets net driver.
[/Script/SteamSockets.SteamSocketsNetDriver]
ConnectionTimeout=60.0
InitialConnectTimeout=120.0