There are lots of tasks that are easily accomplished with bot h PowerShell and T-SQL.
Get-SqlServerKey is a command that will find your product keys. It’s not often you might need this, but it’s a pain to track them down from the registry and be sure you get them for all your instances.
Here’s the view from one of my development machines:
There is a limitation here that appears to have issues with SQL Server 2016, but it’s still helpful for other versions. You can also specify a list of servers in a file for this to use, as well as using credentials to connect.
A quick, handy item, and one that should make auditing (pre-2016) SQL Servers easy.