Ctrl C Ctrl V and works！thank you@Flongo28 is kind of right. Here is how I fixed it for me within the project without specifying an absolute path.

[zlex001]

          @Flongo28 is kind of right. Here is how I fixed it for me within the project without specifying an absolute path.

0. Install the unitypackage if not done already: Rightclick on the Asset Folder in the Project View -> Import Package \ Custom Package -> select cleaner.unitypackage downloaded from this git.
1. Locate the ClassReferenceCollection.cs at <project root dir>\Assets\Cleaner\Editor\ClassReferenceCollection.cs
2. Change the CollectionAllClasses function. There needs to be absolute references, not relative as the LoadFile function gets a.t.m..

Here is what the function should look like:

List<System.Type> CollectionAllClasses ()
{
	List<System.Type> alltypes = new List<System.Type> ();
	string projectPath = Path.GetDirectoryName(Application.dataPath);
	string assemblyPath = Path.Combine(projectPath, "Library/ScriptAssemblies/Assembly-CSharp.dll");
	if (File.Exists(assemblyPath)) {
		alltypes.AddRange(Assembly.LoadFile(assemblyPath).GetTypes()); 
	}
	if (isSaveEditorCode)
	{
		string editorAssemblyPath = Path.Combine(projectPath, "Library/ScriptAssemblies/Assembly-CSharp-Editor.dll");

		if (File.Exists(editorAssemblyPath))
			alltypes.AddRange(Assembly.LoadFile(editorAssemblyPath).GetTypes());
	}
	return alltypes	.ToList ();
}

You may copy and overwrite your definition with the given code.

3. If not done so, make a backup of your asset and library folder! It killed all urp shaders because i did not uncheck them in the process.

4. Save and go back to the Editor -> Window -> Delete Unused Settings.

5. Profit.

I do not have the time to make this a pull request. If someone does so, I would highly appreciate that.

Originally posted by @MatthiasPopp in #3 (comment)