Sorry to come back to the “Deployment health check” dashboard, It is not clear to me why the below “Expired Computers” view doesn’t fit your requirement. If you expand the “Expired Computers” you get a list of not reporting computers. The “Duplicated Computers” also shows the list of computers having more instances in the console. If you combine those two information you can find the “actual” not longer responding computers.
What is missing from there, that you would like to see ?