Thanks @dostovel , it seems to be something like that.
If I mix (diffuse-black rough=1.0) with ((glossy-white rough=1.0) x 0.04) I see something very similar to Principled.
I’ve been trying (in the spirit of the challenge) to change materials/textures only, not touching anything else. I guess what I am seeing is “correct”, even though a little confusing. I guess I can live with it, or dig deeper into lighting/color adjustments…
