C#'s System.Text.Json has weird handling for quotes. This makes it behave more like Newtonsoft.

CSharpJSONQuoteHandling.cs

using System;
using System.Text.Encodings.Web;
using System.Text.Json;

namespace JSONStuff
{
    class Program
    {
        static void Main(string[] args)
        {
            var options = new JsonSerializerOptions
            {
                Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
                WriteIndented = true
            };

            var stringWithQuotes = @" ""Cheese"" is cool";
            var escapedStringWithQuotes = JsonSerializer.Serialize<string>(stringWithQuotes, options);
            Console.WriteLine(escapedStringWithQuotes);

            var unescapedStringWithQuotes = JsonSerializer.Deserialize<string>(escapedStringWithQuotes, options);

            Console.WriteLine(unescapedStringWithQuotes);

        }
    }
}