Everytime I create a new project and import a new Prototype package from Unity Learnings, everything is coated with this pink materials

Unity Engine
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Screenshot (103)
Screenshot (103)1366×768 136 KB

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Run the Render Pipeline converter. I think this is under Window => Rendering or Edit/Assets.

These are likely BiRP assets from older projects. Unity 6 now defaults to URP but you can still create BiRP projects.

URP = Universal Render Pipeline
BiRP = Built-In RP (legacy)