Have done a bunch of research, but there doesn't seem to be a way to set a default audio device in Windows via GPO or registry setting. Has anyone tried this is Kaseya at all? Have a set of conference room PCs that they want it set to the USB device all the time.
You could use a powershell script (executed as you prefer via GPO or using Kaseya).
For that you will need an extension though (but it is a single file easy to deploy and comes with source code so you may also extract the part that you need only and make a simpler function to run on Powershell without extension.
You will find the dll and source code below.
There's also a possible alternative using nircmd (but there's no source code)