Hi,
I’ve made myself a mastermaterial as a material that has options to switch subsurface on/off or clearcoat on/off, and then use those parameters of course. I did so by setting the shading model in the material attributes. Now I’ve copied the whole material over to a material layer to be able to layer it together. The ‘base’ material now just is a simple Material Attribute Layers node that connects to the material attributes of the material. So nothing going on there. If I instance the ‘base’ material and use my material layer, I can’t for the life of me figure out why the shading model doesn’t change. It’s wired up correctly, as it’s a straight copy from a normal material to a material layer and it works as a ‘normal’ material. Are there any weird shenanigans going on with the layering that cause the shading model to disappear? I also set the ‘base’ material to ‘from material expression’ of course 
Kind regards,
Bart