Hello. I used this asset a few months ago when I was learning Unity and it worked just fine. I have attempted to use it now, and I receive the same error every time.

Assets\Tilemap\Rule Tiles\Rule Override Tile\ExampleSiblingRuleTile.cs(5,39): error CS0246: The type or namespace name 'RuleTile' could not be found (are you missing a using directive or an assembly reference?)

There are a few others of the same ilk. I have attempted to manually add it by the package manager, and when I have attempted that I receive either
"[Package Manager] Please select a valid package.json file in a package folder.
UnityEditor.GenericMenu:CatchMenu (object,string[],int)"

Or

"[Package Manager Window] Unable to add package [https://github.com/Unity-Technologies/2d-techdemos.git]:
[https://github.com/Unity-Technologies/2d-techdemos.git] does not point to a valid package repository. No package manifest was found. Verify the repository URL and make sure the package is located in the root folder of the repository.
UnityEditor.EditorApplication:Internal_CallUpdateFunctions ()"

Please assist.