Cannot deserialize decimal with MessagePack and System.Text.Json

[Sire]

Blazor.Extensions.SignalR cannot deserialize decimals using Blazor preview 9 (and System.Text.Json).

To reproduce, just add a decimal to the DemoData class in the test project and enable MessagePack:
In ChatComponent.cs add: opt.EnableMessagePack = true;
In (server) Startup.cs uncomment: .AddMessagePackProtocol();

Any ideas on how to fix this problem? I suspect it's because MessagePack and System.Text.Json are currently incompatible. Possibly related System.Text.Json bug.

A possible fix is to use switch to Newtonsoft instead of the new default System.Text.Json. Previous versions of Blazor.Extensions.SignalR and Blazor 0.9.0 worked fine when used with Newtonsoft as Json serializer. Any way we can make the extension method AddNewtonsoftJsonProtocol work again? Used on
.HubConnectionBuilder(JSRuntimeCurrent).WithUrl("/chathub", options).AddNewtonsoftJsonProtocol();

Exception:

blazor.webassembly.js:1 Uncaught (in promise) Error: System.Text.Json.JsonException: The JSON value could not be converted to System.Decimal. Path: $.Dec | LineNumber: 0 | BytePositionInLine: 42. ---> System.InvalidOperationException: Cannot get the value of a token type 'String' as a number.
  at System.Text.Json.Utf8JsonReader.TryGetDecimal (System.Decimal& value) <0x25a5d98 + 0x0002c> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.Utf8JsonReader.GetDecimal () <0x25a5cc0 + 0x0000a> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.Serialization.Converters.JsonConverterDecimal.Read (System.Text.Json.Utf8JsonReader& reader, System.Type typeToConvert, System.Text.Json.JsonSerializerOptions options) <0x25a5c08 + 0x00004> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.JsonPropertyInfoNotNullable`4[TClass,TDeclaredProperty,TRuntimeProperty,TConverter].OnRead (System.Text.Json.JsonTokenType tokenType, System.Text.Json.ReadStack& state, System.Text.Json.Utf8JsonReader& reader) <0x25a59d0 + 0x00070> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.JsonPropertyInfo.Read (System.Text.Json.JsonTokenType tokenType, System.Text.Json.ReadStack& state, System.Text.Json.Utf8JsonReader& reader) <0x20b7938 + 0x00098> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.JsonSerializer.HandleValue (System.Text.Json.JsonTokenType tokenType, System.Text.Json.JsonSerializerOptions options, System.Text.Json.Utf8JsonReader& reader, System.Text.Json.ReadStack& state) <0x20b70c0 + 0x000d0> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.JsonSerializer.ReadCore (System.Text.Json.JsonSerializerOptions options, System.Text.Json.Utf8JsonReader& reader, System.Text.Json.ReadStack& readStack) <0x20b3ee8 + 0x000a0> in <81e9245ca982431695a55cc67ffb3b86>:0 
   --- End of inner exception stack trace ---
  at System.Text.Json.ThrowHelper.ReThrowWithPath (System.Text.Json.ReadStack& readStack, System.Text.Json.Utf8JsonReader& reader, System.Exception ex) <0x25ef9d0 + 0x00028> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.JsonSerializer.ReadCore (System.Text.Json.JsonSerializerOptions options, System.Text.Json.Utf8JsonReader& reader, System.Text.Json.ReadStack& readStack) <0x20b3ee8 + 0x00340> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.JsonSerializer.ReadCore (System.Type returnType, System.Text.Json.JsonSerializerOptions options, System.Text.Json.Utf8JsonReader& reader) <0x20a9df0 + 0x0003e> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.JsonSerializer.ParseCore (System.String json, System.Type returnType, System.Text.Json.JsonSerializerOptions options) <0x20a5b00 + 0x00086> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at System.Text.Json.JsonSerializer.Deserialize[TValue] (System.String json, System.Text.Json.JsonSerializerOptions options) <0x2591390 + 0x00022> in <81e9245ca982431695a55cc67ffb3b86>:0 
  at Blazor.Extensions.HubConnection+<>c__DisplayClass30_0`10[TResult1,TResult2,TResult3,TResult4,TResult5,TResult6,TResult7,TResult8,TResult9,TResult10].<On>b__0 (System.String[] payloads) <0x25910d0 + 0x000a8> in <c55a512ad88d4b5691739ffb720e5e8d>:0 
  at (wrapper delegate-invoke) System.Func`2[System.String[],System.Threading.Tasks.Task].invoke_TResult_T(string[])
  at Blazor.Extensions.HubMethodCallback.On (System.String[] payloads) <0x2505058 + 0x00014> in <c55a512ad88d4b5691739ffb720e5e8d>:0 
  at (wrapper managed-to-native) System.Reflection.RuntimeMethodInfo.InternalInvoke(System.Reflection.RuntimeMethodInfo,object,object[],System.Exception&)
  at System.Reflection.RuntimeMethodInfo.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) <0x1c128d0 + 0x000d2> in <b455df9113dd49c5bfed215a721aae19>:0 
--- End of stack trace from previous location where exception was thrown ---

  at Microsoft.JSInterop.Infrastructure.DotNetDispatcher.InvokeSynchronously (Microsoft.JSInterop.JSRuntime jsRuntime, Microsoft.JSInterop.Infrastructure.DotNetInvocationInfo& callInfo, Microsoft.JSInterop.Infrastructure.IDotNetObjectReference objectReference, System.String argsJson) <0x21d7068 + 0x0018a> in <b57783c7fafa47088562351a82800d2f>:0 
  at Microsoft.JSInterop.Infrastructure.DotNetDispatcher.BeginInvokeDotNet (Microsoft.JSInterop.JSRuntime jsRuntime, Microsoft.JSInterop.Infrastructure.DotNetInvocationInfo invocationInfo, System.String argsJson) <0x2246838 + 0x000ba> in <b57783c7fafa47088562351a82800d2f>:0 
    at Object.endInvokeDotNetFromJS (http://localhost:61448/_framework/blazor.webassembly.js:1:7164)
    at Object.invokeJSFromDotNet (http://localhost:61448/_framework/blazor.webassembly.js:1:6790)
    at _mono_wasm_invoke_js_marshalled (http://localhost:61448/_framework/wasm/mono.js:1:176158)
    at wasm-function[6322]:0x129810
    at wasm-function[1962]:0x6063e
    at wasm-function[565]:0x12891
    at wasm-function[565]:0x12eca
    at wasm-function[565]:0x12c35
    at wasm-function[565]:0x12c35
    at wasm-function[565]:0x12eca

[galvesribeiro]

Check the latest package as it is working as expected.