Is there a material library in Blender 2.8 (eevee)? - Materials and Textures - Blender Artists Community
CG Cookie - New in Blender 3.0: the long awaited Asset Browser! ✓ currently only supports objects, materials, poses, and worlds ✓ you can drag & drop assets into any scene ✓
File Browser — Blender Manual
Materio Asset Pack - Blender Market
Material Browser — Omniverse Extensions documentation