A converter for `System.Text.Json` that recursively parse converts json to the inferred types. Uses `ExpandoObject` for objects.

ObjectToInferredTypesConverter.cs

using System.Text.Json;
using System.Text.Json.Serialization;
using System.Dynamic;

public class ObjectToInferredTypesConverter : JsonConverter<object>
{
    public override object Read(
        ref Utf8JsonReader reader,
        Type typeToConvert,
        JsonSerializerOptions options) =>
        reader.TokenType switch
        {
            JsonTokenType.True => true,
            JsonTokenType.False => false,
            JsonTokenType.Number when reader.TryGetInt64(out long l) => l,
            JsonTokenType.Number => reader.GetDouble(),
            JsonTokenType.String when reader.TryGetDateTime(out DateTime datetime) => datetime,
            JsonTokenType.String => reader.GetString(),
            JsonTokenType.StartObject => JsonSerializer.Deserialize<ExpandoObject>(ref reader, options),
            JsonTokenType.StartArray => JsonSerializer.Deserialize<IList<object>>(ref reader, options),
            _ => JsonDocument.ParseValue(ref reader).RootElement.Clone()
        };

    public override void Write(
        Utf8JsonWriter writer,
        object objectToWrite,
        JsonSerializerOptions options) =>
        throw new InvalidOperationException("Not meant for serialization.");
}