MSIX Core is a way to have your MSIX packages run on older versions of Windows. While not retaining all features (including security, delivery optimization and several others which are exclusive to Windows 10 supported builds) they are still installable and provide a bridge experience and a single deployment (same MSIX package) for both modern and legacy systems.
In order to enable support for MSIX Core, a dependency on the target platform MSIXCore. Desktop is required. You can configure it in the Dependencies screen:
