Is there any way I can use Companion on a Windows 10 PC?
Not officially. Although on Windows 11 it’s possible to access a preview version of the Windows Subsystem for Android, which lets you run Android apps. I haven’t tried this myself to see if Companion works like that.
Do you not have another device, e.g. a phone, to run ZC on?
The requirements for a device to run the Companion App are pretty low so if you have an old smartphone lying around the chances are pretty good it will do the trick. Additionally, since the device running the Companion app has to be on wifi to sync up for game mode, there’s no requirement for active phone service on the device.