[Zubersoft]

Yes, unfortunately that is the case. Or you can use a Windows VM with free software like VirtualBox to run the companion app in, and then you can connect that to MobileSheets. In the future, once I switch MobileSheets from a UWP application back to a standard desktop application, this will restriction will vanish and it will be possible to run the companion app on the same machine. As a side note, with the Windows version of MobileSheets, you don't really need the companion, and anything you can do in the companion you can do in the Windows version itself.

Mike