You could try my converter: https://gum.co/q2s It was tested with default materials, but it will handle custom ones too, I believe. It don't export megascans, though.
I tried exporting a new material I made in Quixel DDO into Substance Painter and needless to say it did not work... I read that I am supposed to export it as a bitmap and Disney GGX file and when I did it looked like this: This is not right, when I click the dropdown under undefined it does not say material. When I import…