I get the warning from package validator:
Each mesh should have a corresponding prefab set up with all variations of the texture/mesh/material that you are providing. Please create prefabs for all of your imported objects.
I couldn’t get rid of the warning, so I opened a brand new project, imported the default cube (without camera and light) from blender, created a prefab for it. The warning still exists. There is nothing else in the folder.
I didn’t change anything on the cube in Blender, kept the default FBX export settings and the default import settings in Unity. Created a new prefab, a prefab variant of the imported model, both with the material inside the model and a brand new material inside the folder I am testing.
Tested with Unity 2018.4.10f1, 2019.2.5f1, 2019.3.0f3
Am I missing something about what the warning means? Any help would be appreciated.