Lync 2010 Decommission

Hi,
I am Rubiat.
I am working in a vendor which is a Microsoft solution partner. I have faced a problem recently. One of my customer wants to fully decommission Lync 2010 from their environment. All of their users are now using Microsoft Teams. They have a lot of front end and back end servers. Approximately the number of servers is nearly about 43. But maximum servers are down for 3-4 years. When I engaged to decommission Lync, I saw the backend servers are not found. Then he told me that some one remove the servers from Hyper-V.
Now, could anyone please tell me, is there have an another way to decommission Lync 2010 from existing environment by removing registry value? If possible then could anyone please share the registry values?
Thank You