Latest Prism does not have support of MEF as DI container for UWP projects.At present unity and autofac are available DI containers for UWP Application.
Microsoft Composition (MEF 2) provide a Portable class library version of the Managed Extensibility Framework (MEF) that is lightweight and specifically optimized for high throughput.
Nuget package available for this MEF: Microsoft.Composition (MEF2 1.0.30).
If we provide MEF container concept for UWP, traditional WPF Applications which are MEF based will have more flexibility to move to UWP.
Can we use this portable class library and use MEF with Prism6 UWP and derive some MEF container concepts for UWP?
Of course you can. You just have to create an assembly that has support for your desired version of MEF. You can use one of the existing projects as a blueprint on how to create yours:
https://github.com/PrismLibrary/Prism/tree/master/Source/Windows10/Prism.Unity.Windows