@jsheehan:Thanks for the link. As far as I can tell, old-school COM based tools like VFP and VB6 don't have access to the WinRT API, so they won't be able to work directly with AppService to communicate with the UWP app. Is that a scenario you are wanting to support?
This looks promising. On the desktop side of things, is a COM API available for App Service to communicate with the UWP app? If there is a link with more info on that, please point me to it. Also, has your team done any testing with Visual FoxPro?
This is a great session. It clearly describes and demonstrates the various options you have for getting your apps on multiple devices. Well worth your time if you're trying to figure out what approach you want to take.