Error CS0246 in Editor Scripts

Do you need this package? If so you will need to find and satisfy its dependencies.

Otherwise, remove it.

Extra unwanted packages in new projects (collab, testing, rider and other junk):

About the fastest way I have found to make a project and avoid all this noise is to create the project, then as soon as you see the files appear, FORCE-STOP (hard-kill) Unity (with the Activity Manager or Task Manager), then go hand-edit the Packages/manifest.json file as outlined in the above post, then reopen Unity.

Sometimes the package system gets borked from all this unnecessary churn and requires the package cache to be cleared: