Unity-Technologies
@@ -1092,7 +1092,10 @@ internal static void ResetSingleton()
         /// </summary>
         public void SetSingleton()
         {
-            Singleton = this;
+            if (!Singleton || !Singleton.IsServer)
+            {
+                Singleton = this;
+            }
 
             OnSingletonReady?.Invoke();
         }
@@ -1401,7 +1404,14 @@ internal void InitializeNetcodeWorld()
             /// !! Initialize worlds here !!
             /// Worlds are created here: <see cref="UnifiedBootStrap.Initialize"/>
             UnifiedBootstrap.CurrentNetworkManagerForInitialization = this;
-            DefaultWorldInitialization.Initialize("Default World", false);
+            if (UnifiedBootstrap.Instance != null)
+            {
+                UnifiedBootstrap.Instance.Initialize("Default World");
+            }
+            else
+            {
+                DefaultWorldInitialization.Initialize("Default World", false);
+            }
         }
 
         /// <summary>

@@ -3736,7 +3736,13 @@ private void Start()
 
         private void InitGhost()
         {
-            if (!NetworkManager.IsListening)
+            if (!HasGhost || !NetworkObjectBridge || GhostAdapter.IsPrefab())
+            {
+                // Nothing to register
+                return;
+            }
+
+            if (!NetworkManager || !NetworkManager.IsListening)
             {
                 if (NetworkManager.LogLevel == LogLevel.Developer)
                 {
@@ -3745,12 +3751,6 @@ private void InitGhost()
                 return;
             }
 
-            if (!HasGhost || !NetworkObjectBridge || GhostAdapter.IsPrefab())
-            {
-                // Nothing to register
-                return;
-            }
-
             // All instances with Ghosts are automatically registered
             if (NetworkManager.LogLevel == LogLevel.Developer)
             {

@@ -2449,14 +2449,6 @@ internal void SpawnInstanceWithOwnership(NetworkObject networkObjectToSpawn, Net
             }
             else
             {
-#if UNIFIED_NETCODE
-                // TODO-FixMe: NetCode.Netcode.Instance is a singleton and might cause issues
-                // assigning this.
-                if (networkObjectToSpawn.HasGhost)
-                {
-                    NetCode.Netcode.Instance.m_ActiveWorld = m_ServerNetworkManager.NetcodeWorld;
-                }
-#endif
                 networkObjectToSpawn.NetworkManagerOwner = m_ServerNetworkManager; // Required to assure the server does the spawning
                 if (spawnAuthority == m_ServerNetworkManager)
                 {

@@ -1,6 +1,9 @@
 using System.Collections.Generic;
 using Unity.Netcode;
 using UnityEngine;
+#if UNIFIED_NETCODE
+using Unity.NetCode;
+#endif
 
 namespace TestProject.RuntimeTests
 {

@@ -15,7 +15,8 @@
         "Unity.Mathematics",
         "UnityEngine.TestRunner",
         "UnityEditor.TestRunner",
-        "Unity.Netcode.Runtime.Tests"
+        "Unity.Netcode.Runtime.Tests",
+        "Unity.NetCode"
     ],
     "includePlatforms": [],
     "excludePlatforms": [],