I'm working as per this guide
Everything is good up until step #5 which is adding the new Xamarin.iOS library as a reference to my .Net Standard 2.0 main project. But I could not add it because of an (Incompatible target framework. Xamarin.iOS version=v1.0) error.
@JoeManke advised me to add the iOS library to the iOS project and then use it through dependency injection within the main project. However as I implemented this workaround and moved forward to step #6 I found that all models that will be moved to the new library will be under an unaccessible namespace to the shared project where all the work is being done.