After upgrading to latest XCode and Xamarin, when building in Visual Studio, I can no longer target any iOS devices older than 11. What happened?
If you want to build against iOS 10 frameworks, you would need to use Xcode 8 by setting the Xamarin's Apple SDK to point to a copy of Xcode 8.
Now via the Deployment Target
within the Info.plist you can control what is the minimum iOS version that you want your app to run against.
The Deployment Target setting is used to select the minimum required version of the operating system on which your application will run. This is set in your Project's Info.plist file. You should pick the minimum version that has all the APIs that you need to run your application.
For a Forms-based Xamarin.iOS
you do not want to set the min. to less then iOS 8
Xamarin.Forms applications can be written for the following operating systems: