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Microsoft is blocking Windows Customization Tools
(www.neowin.net)
This is a most excellent place for technology news and articles.
Its something happened waaay back during the technical preview days. Just like with this instance, the workaround was to rename the installer executable.
https://winaero.com/microsoft-to-block-classic-shell-in-windows-10-here-is-why/
And I think you should update to OpenShell at least.