EDIT:
Xamarin.Insights will provide exception reporting from your core project without an explicit reference, but if you are doing any explicit Insights reporting calls in the core project, you'll leave that reference alone.
Insights did change a while back to have platform-specific initialization though, as the error indicates.
If you add a reference to your Xamarin.iOS and Xamarin.Android projects, things should work as before, once you move the Insights initialization into each platform-specific startup.
Here is an App class from a Xamarin.iOS project that shows the Xamarin.Insights initialization:
public class App
{
private static void Main(string[] args)
{
// Initialize metrics and crash tracking.
Xamarin.Insights.Initialize(Forms.App.XamarinInsightsApiKey);
// Launch UI.
UIApplication.Main(args, null, "AppDelegate");
}
}
And the Xamarin.Android version:
[Application]
public class MainApplication : Application, Application.IActivityLifecycleCallbacks
{
#region Constructors
public MainApplication(IntPtr handle, JniHandleOwnership transer)
:base(handle, transer)
{
// Do not remove this work-around for a Xamarin linker issue related to SSL/TLS certificate trust. This line of
// code prevents the linker from stripping out AES capabilities needed but not obvious because they are accessed
// via reflection. Issue https://bugzilla.xamarin.com/show_bug.cgi?id=13998.
// ReSharper disable once UnusedVariable
var b = new System.Security.Cryptography.AesCryptoServiceProvider();
NotificationToken = null;
}
#endregion Constructors
#region Methods
public override void OnCreate()
{
base.OnCreate();
RegisterActivityLifecycleCallbacks(this);
// Initialize metrics and crash tracking.
Xamarin.Insights.Initialize(Forms.App.XamarinInsightsApiKey, ApplicationContext);
}