In terms of telemetry, free software has the advantage over the proprietary counterpart.
It’s a lot more complicated to hide telemetry without the user knowing in free software.
You could always use a network tool, like iftop, to see network traffic on your PC. That could be a way too see if a program is phoning home. But you’ll probably want to use a suite of tools.





What country/region are you in?
In the North America, I’d recommend Novelkeys, Omnitype, Mekibo, Cannonkeys and spacecables (spaceholdings) for GMK sets
A better approach is to keep your eyes out on Geekhack. The majority of keyboards and keycaps go through an interest check there, and then the designer announces all regional vendors/prices prior to a groupbuy.