My team is writing set of hybrid applications targeting both iOS and Android. We are using our own framework similar to Cordova or PhoneGap. The same team is also writing a .NET Core application expected to run both on Windows and Mac. For the Windows and Mac we created a windows and a mac installer using WiX. The Android and iOS applications are delivered using the Google and Apple Stores.
We are looking for more documentation and examples regarding using MSIX SDK to target non-windows 10 platforms. We are interested in using MSIX for deploying and updating applications anywhere.
@Avanegas For the most part the SDK cross platform is for extensibility right now. We are looking at what it might mean to add a deployment stack to Linux and MacOS. Possibly Android as well, but it would not be supported by Google Play. For iOS it will only be extensions due to the closed nature of the platform.
I don't have any timelines for the above, but remember it is an open repo so anyone can contribute. :)