I can add that for anyone struggling with the AMM0000 Android Exported error in Visual Studio, it need to be added to the WebAuthenticationCallbackActivity file (or manifest I assume) like
[Activity(NoHistory = true, Exported = true, LaunchMode = LaunchMode.SingleTop)]
Lowering Android SKD will also work but perhaps not ideal for other reasons.
@andrea.chiarelli Thanks for a nice sample and article!