Need to find all inactive SQL instances in the domain

Hi, Hoping for some direction, not a complete answer.

I need to find a way to scan the domain for all SQL Server instances, and identify those not in active use.

I thought maybe something like a Power-Shell script that would scan the domain, list all SQL instances along with the active connections, and save the results as an Excel spreadsheet. Any with few active connections would be manually reviewed. However, I'm open to anything.

I'm trying to identify inactive instances for decommissioning on a domain with hundreds of SQL Server installs.

Any ideas on where to start would be appreciated.