From a minimal ASP.NET Core Web API how do I return a JObject while maintaining the nested elements?

I am building a minimal ASP.NET Core Web API. One of my endpoints needs to return data contained in a JObject. This JObject represents a complex nested data structure. What I am finding is that the response from this endpoint loses all of the nested data from the JObject.

From what have read, I suspect this is caused by the fact that by default .NET Core uses its own Json libraries for serialisation and JObect is a Newtonsoft class, but so far I haven't discovered what the best practice is for handling this.

For example, the JObject that I am working with correctly contains all expected key-value data. Some values contain nested data themselves.

If I run .ToString() on it this is what it looks like:

{
  "key": "stringValue",
  "key": "stringValue",
  "key": "stringValue",
  "key": {
    "nestedKey": "nestedValue",
    "nestedKey": "nestedValue"
  },
  "key": "stringValue",
  "key": "stringValue"
  ..
}

The problem is that when I return the JObject like this:

JObject result = service.ParseToJObject(request.Message);
return TypedResults.Ok(result);

The response object looks like this - all the nested values have been lost.

{
  "key1": [],
  "key2": [],
  "key2": [],
   ...
}

I can resolve this issue with the following change (converting the JObject to a string), but want to know if there is a better way to fix this at the global level. With this change the returned object correctly contains all key-value pairs.

string result = service.ParseToJObject(request.Message).ToString();
return TypedResults.Content(result, "application/json");

I've tried various suggestions off the net around setting Json serialization options on the builder (one example below), but none of these have made any difference to the return data.

builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.ReferenceHandler = ReferenceHandler.Preserve;
    options.SerializerOptions.PropertyNameCaseInsensitive = true;
    options.SerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull;
    options.SerializerOptions.Converters.Add(new JsonStringEnumConverter());
});

Thanks