I run on 4.24.1 and, while I can’t see the dedicated server under the Internet tab on Steam, it does successfully initialise and it is shown under Lan tab.
[2020.03.06-07.47.22:065] 0]LogLoad: (Engine Initialization) Total time: 1.04 seconds
[2020.03.06-07.47.23:486] 42]LogNet: Browse: /Game/_Levels/Level1?listen
[2020.03.06-07.47.23:486] 42]LogLoad: LoadMap: /Game/_Levels/Level1?listen
[2020.03.06-07.47.23:487] 42]LogWorld: BeginTearingDown for /Game/_Levels/MainMenu
[2020.03.06-07.47.23:490] 42]LogNet: World NetDriver shutdown SteamNetDriver_2147482586 [GameNetDriver]
[2020.03.06-07.47.23:490] 42]LogNet: DestroyNamedNetDriver SteamNetDriver_2147482586 [GameNetDriver]
[2020.03.06-07.47.23:490] 42]LogExit: GameNetDriver SteamNetDriver_2147482586 shut down
[2020.03.06-07.47.23:491] 42]LogWorld: UWorld::CleanupWorld for MainMenu, bSessionEnded=true, bCleanupResources=true
[2020.03.06-07.47.23:492] 42]LogUObjectHash: Compacting FUObjectHashTables data took 0.60ms
[2020.03.06-07.47.23:553] 42]LogAIModule: Creating AISystem for world Level1
[2020.03.06-07.47.23:554] 42]LogLoad: Game class is 'MultiplayerGameMode_C'
[2020.03.06-07.47.23:556] 42]LogNet: ReplicationDriverClass is null! Not using ReplicationDriver.
[2020.03.06-07.47.23:556] 42]LogNetCore: DDoS detection status: detection enabled: 0 analytics enabled: 0
[2020.03.06-07.47.23:557] 42]LogNet: Display: SteamNetDriver_2147482567 bound to port 7777
[2020.03.06-07.47.23:557] 42]PacketHandlerLog: Loaded PacketHandler component: Engine.EngineHandlerComponentFactory (StatelessConnectHandlerComponent)
[2020.03.06-07.47.23:557] 42]LogNet: GameNetDriver SteamNetDriver_2147482567 IpNetDriver listening on port 7777
[2020.03.06-07.47.23:561] 42]LogWorld: Bringing World /Game/_Levels/Level1.Level1 up for play (max tick rate 30) at 2020.03.06-09.47.23
[2020.03.06-07.47.23:562] 42]LogWorld: Bringing up level for play took: 0.003420
[2020.03.06-07.47.23:562] 42]LogGameMode: Display: Match State Changed from EnteringMap to WaitingToStart
[2020.03.06-07.47.23:563] 42]LogBlueprintUserMessages: [Level1_C_0] Dedicated Server successfully started!
[2020.03.06-07.47.23:565] 42]LogGameState: Match State Changed from EnteringMap to WaitingToStart
[2020.03.06-07.47.23:565] 42]LogLoad: Took 0.079518 seconds to LoadMap(/Game/_Levels/Level1)
My DefaultEngine.ini
[/Script/Engine.Engine]
SmoothedFrameRateRange=(LowerBound=(Type=Inclusive,Value=22.000000),UpperBound=(Type=Exclusive,Value=187.533066))
bSmoothFrameRate=True
!NetDriverDefinitions=ClearArray
+NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="OnlineSubsystemSteam.SteamNetDriver",DriverClassNameFallback="OnlineSubsystemUtils.IpNetDriver")
[OnlineSubsystem]
DefaultPlatformService=Steam
PollingIntervalInMs=20
bHasVoiceEnabled=true
bUsesPresence=false
; Uncomment the following line to use the Null Subsystem
; DefaultPlatformService=Null
VoiceNotificationDelta=0.2
[OnlineSubsystemSteam]
bEnabled=true
SteamDevAppId=480
SteamAppId=480
GameServerQueryPort=27015
bRelaunchInSteam=false
GameVersion=1.0.0.0
bVACEnabled=1
bAllowP2PPacketRelay=true
P2PConnectionTimeout=90
bUsesPresence=false
; This is to prevent subsystem from reading other achievements that may be defined in parent .ini
Achievement_0_Id=""
[/Script/OnlineSubsystemSteam.SteamNetDriver]
NetConnectionClassName="OnlineSubsystemSteam.SteamNetConnection"
;ReplicationDriverClassName="/Script/ShooterGame.ShooterReplicationGraph"
AllowDownloads=false
So the only difference I see is the order and missing value on Achievement_0_Id(not sure if no value is considered as empty string).