It allows you to add your own custom AMP Endpoints as Subdomain.Using this extension you can customize the structure of AMP URL as per your requirement.
It will allow you to add your own Subdomain as an AMP URL (amp.website.com)
It will even allow you to set AMP in the middle of the URL (website.com/amp/article/ )
While Placing the Subdomain you can use any custom subdomain name.
Very easy setup you just need to set your custom endpoint.
We do have an option which allows you to enable/disable the endpoint support for your Websites. Once you set your custom endpoint and after saving the permalinks the url will be changed as per your set-up.