TypeLoadException: Could not resolve type with token 01000149 (from typeref, class/assembly UnityEditor.SceneManagement.PrefabStage, UnityEditor, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null)
So the story here is I was fixing some package conflicts, all of it is solved now, but I removed an asset and started resolving some script assemblies, it took a lot of time 30mins, I search the internet why is it that, said its a bug at my version (2020.3.37f1)
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: