I created a *NEW* project with the URP and brought in all of my assets. I then has Unity create new materials for them by using "Edit->Render Pipeline->Universal Render Pipeline->Upgrade Project Materials to UniversalRP Materials". When I add the prefabs to the project they display properly, but in Project window, the previews of these prefabs are (mostly) pink. Some prefabs appear to manually be previewing properly, but the vast majority of them are pink. I have tried having Unity reimport everything, but that does nothing useful. Any thoughts?