Hello,
I see a legacy conversion node on that graph: are you sure you have not enabled Substrate for that project, saved the converted material and then disabled Substrate? Because Substrate is not backward compatible as mentioned in the documentation. Once the conversion node is added and the material saved, all previous links and setup are gone.
If that is not what you did and if there really are some Quixel MS material using Substrate once downloaded, then please report which one. That would be a mistake.
Thanks.