At least try and see if it solves your issue. And if it does, please submit a PR to the Neos GraphQL package that explains that needed installation setup
So, what’s the acutal respons of your request? If you click preview instead of headers on your latest screenshot you should see the error message. “Unexpected token < in …” just inidicates that graphql playground could not parse the response to json. As you pointed out it’s text/html. And in that request the error is printed out.
I had solved this long back and now I am into the different account where leveraging the other framework.
you may please contact me online I can help you on this