Async IAsyncEnumerable using Newtonsoft in ASP.net

Question

I have a asp.net application that uses

builder.Services.AddControllers()
    .AddNewtonsoftJson();

This causes the return of the controller not to run asynchronous

        [HttpGet("IAsyncTest")]
        public IAsyncEnumerable<TestDTO> GetTestValue()
        {
            return _getValues();
        }

        private static readonly TestDTO[] _values = new[]
        {
            new TestDTO {IntValue= 1, StringValue = "Value 1"},
            new TestDTO {IntValue= 2, StringValue = "Value 2"},
            new TestDTO {IntValue= 3, StringValue = "Value 3"},
            new TestDTO {IntValue= 4, StringValue = "Value 4"},
            new TestDTO {IntValue= 5, StringValue = "Value 5"},
        };

        private async IAsyncEnumerable<TestDTO> _getValues()
        {
            foreach (var value in _values)
            {
                yield return value;
                await Task.Delay(TimeSpan.FromSeconds(20));
            }
        }

Is there a way to use Newtonsoft only in certain controllers not all of them? Or specify which controller uses Text.Json.

Or Is it possible to create a custom formatter that uses that Text.Json for IAsyncEnumerable.

Code example is here: GitHub Link

Thanks for helping