Here are some CC0 Free Mats you can use however you like. I encourage you to use these when creating KPACKS of INSERTS you may want to distribute or sell, as then they'll match other KPACKS and the user need only edit one material to change all of them in a scene.
https://filedn.com/lLMW4jXsJqxXkRYjd1UCoKL/SYNTHbeta/CW-Free-Mats.zip
Unlike EEVEE Materials System "EMS" (which is not free), these materials contain no images and are 100% procedural. So, there is little to no filesize overhead.
And, as we're talking about free, we have a new policy on the use of INSERTS to create commercial KPACKS which is less restrictive:
Feel free to use our INSERTS to create other commercial INSERTS as long as:
1. You don't use our EMS materials
2. You don't use our labels and decal INSERTS.
3. The INSERTS you do use are geometry only and not the primary part of your INSERT.