diff --git a/osu.Game/Online/API/APIAccess.cs b/osu.Game/Online/API/APIAccess.cs
index 525eb98a86..54eed58c13 100644
--- a/osu.Game/Online/API/APIAccess.cs
+++ b/osu.Game/Online/API/APIAccess.cs
@@ -409,8 +409,8 @@ namespace osu.Game.Online.API
             SecondFactorCode = code;
         }
 
-        public IHubClientConnector GetHubConnector(string clientName, string endpoint, bool preferMessagePack) =>
-            new HubClientConnector(clientName, endpoint, this, versionHash, preferMessagePack);
+        public IHubClientConnector GetHubConnector(string clientName, string endpoint) =>
+            new HubClientConnector(clientName, endpoint, this, versionHash);
 
         public IChatClient GetChatClient() => new WebSocketChatClient(this);
 
diff --git a/osu.Game/Online/API/DummyAPIAccess.cs b/osu.Game/Online/API/DummyAPIAccess.cs
index 0c2ed9903c..74e0ca2873 100644
--- a/osu.Game/Online/API/DummyAPIAccess.cs
+++ b/osu.Game/Online/API/DummyAPIAccess.cs
@@ -185,7 +185,7 @@ namespace osu.Game.Online.API
         {
         }
 
-        public IHubClientConnector? GetHubConnector(string clientName, string endpoint, bool preferMessagePack) => null;
+        public IHubClientConnector? GetHubConnector(string clientName, string endpoint) => null;
 
         public IChatClient GetChatClient() => new TestChatClientConnector(this);
 
diff --git a/osu.Game/Online/API/IAPIProvider.cs b/osu.Game/Online/API/IAPIProvider.cs
index 3ab985e41f..2634ea137f 100644
--- a/osu.Game/Online/API/IAPIProvider.cs
+++ b/osu.Game/Online/API/IAPIProvider.cs
@@ -138,8 +138,7 @@ namespace osu.Game.Online.API
         /// </summary>
         /// <param name="clientName">The name of the client this connector connects for, used for logging.</param>
         /// <param name="endpoint">The endpoint to the hub.</param>
-        /// <param name="preferMessagePack">Whether to use MessagePack for serialisation if available on this platform.</param>
-        IHubClientConnector? GetHubConnector(string clientName, string endpoint, bool preferMessagePack = true);
+        IHubClientConnector? GetHubConnector(string clientName, string endpoint);
 
         /// <summary>
         /// Accesses the <see cref="INotificationsClient"/> used to receive asynchronous notifications from web.
diff --git a/osu.Game/Online/HubClientConnector.cs b/osu.Game/Online/HubClientConnector.cs
index 9288a32052..e6391e8810 100644
--- a/osu.Game/Online/HubClientConnector.cs
+++ b/osu.Game/Online/HubClientConnector.cs
@@ -2,14 +2,11 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
-using System.Collections.Generic;
 using System.Net;
-using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.SignalR.Client;
 using Microsoft.Extensions.DependencyInjection;
-using Newtonsoft.Json;
 using osu.Framework;
 using osu.Game.Online.API;
 
@@ -29,7 +26,6 @@ namespace osu.Game.Online
 
         private readonly string endpoint;
         private readonly string versionHash;
-        private readonly bool preferMessagePack;
 
         /// <summary>
         /// The current connection opened by this connector.
@@ -43,14 +39,12 @@ namespace osu.Game.Online
         /// <param name="endpoint">The endpoint to the hub.</param>
         /// <param name="api"> An API provider used to react to connection state changes.</param>
         /// <param name="versionHash">The hash representing the current game version, used for verification purposes.</param>
-        /// <param name="preferMessagePack">Whether to use MessagePack for serialisation if available on this platform.</param>
-        public HubClientConnector(string clientName, string endpoint, IAPIProvider api, string versionHash, bool preferMessagePack = true)
+        public HubClientConnector(string clientName, string endpoint, IAPIProvider api, string versionHash)
             : base(api)
         {
             ClientName = clientName;
             this.endpoint = endpoint;
             this.versionHash = versionHash;
-            this.preferMessagePack = preferMessagePack;
 
             // Automatically start these connections.
             Start();
@@ -78,26 +72,10 @@ namespace osu.Game.Online
                     options.Headers.Add(CLIENT_SESSION_ID_HEADER, API.SessionIdentifier.ToString());
                 });
 
-            if (RuntimeFeature.IsDynamicCodeCompiled && preferMessagePack)
+            builder.AddMessagePackProtocol(options =>
             {
-                builder.AddMessagePackProtocol(options =>
-                {
-                    options.SerializerOptions = SignalRUnionWorkaroundResolver.OPTIONS;
-                });
-            }
-            else
-            {
-                // eventually we will precompile resolvers for messagepack, but this isn't working currently
-                // see https://github.com/neuecc/MessagePack-CSharp/issues/780#issuecomment-768794308.
-                builder.AddNewtonsoftJsonProtocol(options =>
-                {
-                    options.PayloadSerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
-                    options.PayloadSerializerSettings.Converters = new List<JsonConverter>
-                    {
-                        new SignalRDerivedTypeWorkaroundJsonConverter(),
-                    };
-                });
-            }
+                options.SerializerOptions = SignalRUnionWorkaroundResolver.OPTIONS;
+            });
 
             var newConnection = builder.Build();
 
diff --git a/osu.Game/Online/Metadata/OnlineMetadataClient.cs b/osu.Game/Online/Metadata/OnlineMetadataClient.cs
index 366ad70db2..6402962e85 100644
--- a/osu.Game/Online/Metadata/OnlineMetadataClient.cs
+++ b/osu.Game/Online/Metadata/OnlineMetadataClient.cs
@@ -56,7 +56,7 @@ namespace osu.Game.Online.Metadata
         {
             // Importantly, we are intentionally not using MessagePack here to correctly support derived class serialization.
             // More information on the limitations / reasoning can be found in osu-server-spectator's initialisation code.
-            connector = api.GetHubConnector(nameof(OnlineMetadataClient), endpoint, false);
+            connector = api.GetHubConnector(nameof(OnlineMetadataClient), endpoint);
 
             if (connector != null)
             {
diff --git a/osu.Game/Online/SignalRDerivedTypeWorkaroundJsonConverter.cs b/osu.Game/Online/SignalRDerivedTypeWorkaroundJsonConverter.cs
deleted file mode 100644
index 86708bee82..0000000000
--- a/osu.Game/Online/SignalRDerivedTypeWorkaroundJsonConverter.cs
+++ /dev/null
@@ -1,61 +0,0 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
-// See the LICENCE file in the repository root for full licence text.
-
-using System;
-using System.Linq;
-using Newtonsoft.Json;
-using Newtonsoft.Json.Linq;
-
-namespace osu.Game.Online
-{
-    /// <summary>
-    /// A type of <see cref="JsonConverter"/> that serializes a subset of types used in multiplayer/spectator communication that
-    /// derive from a known base type. This is a safe alternative to using <see cref="TypeNameHandling.Auto"/> or <see cref="TypeNameHandling.All"/>,
-    /// which are known to have security issues.
-    /// </summary>
-    public class SignalRDerivedTypeWorkaroundJsonConverter : JsonConverter
-    {
-        public override bool CanConvert(Type objectType) =>
-            SignalRWorkaroundTypes.BASE_TYPE_MAPPING.Any(t =>
-                objectType == t.baseType ||
-                objectType == t.derivedType);
-
-        public override object? ReadJson(JsonReader reader, Type objectType, object? o, JsonSerializer jsonSerializer)
-        {
-            if (reader.TokenType == JsonToken.Null)
-                return null;
-
-            JObject obj = JObject.Load(reader);
-
-            string type = (string)obj[@"$dtype"]!;
-
-            var resolvedType = SignalRWorkaroundTypes.BASE_TYPE_MAPPING.Select(t => t.derivedType).Single(t => t.Name == type);
-
-            object? instance = Activator.CreateInstance(resolvedType);
-
-            if (instance != null)
-                jsonSerializer.Populate(obj["$value"]!.CreateReader(), instance);
-
-            return instance;
-        }
-
-        public override void WriteJson(JsonWriter writer, object? o, JsonSerializer serializer)
-        {
-            if (o == null)
-            {
-                writer.WriteNull();
-                return;
-            }
-
-            writer.WriteStartObject();
-
-            writer.WritePropertyName(@"$dtype");
-            serializer.Serialize(writer, o.GetType().Name);
-
-            writer.WritePropertyName(@"$value");
-            writer.WriteRawValue(JsonConvert.SerializeObject(o));
-
-            writer.WriteEndObject();
-        }
-    }
-}
diff --git a/osu.Game/Online/SignalRWorkaroundTypes.cs b/osu.Game/Online/SignalRWorkaroundTypes.cs
index 757bb07ec8..6ae178e04c 100644
--- a/osu.Game/Online/SignalRWorkaroundTypes.cs
+++ b/osu.Game/Online/SignalRWorkaroundTypes.cs
@@ -14,7 +14,6 @@ namespace osu.Game.Online
     /// A static class providing the list of types requiring workarounds for serialisation in SignalR.
     /// </summary>
     /// <seealso cref="SignalRUnionWorkaroundResolver"/>
-    /// <seealso cref="SignalRDerivedTypeWorkaroundJsonConverter"/>
     internal static class SignalRWorkaroundTypes
     {
         internal static readonly IReadOnlyList<(Type derivedType, Type baseType)> BASE_TYPE_MAPPING = new[]