How to fix the Android.Auth Version Conflict
The following link describes the problem and a potential solution: https://github.com/xamarin/Xamarin.Auth/issues/294
Solution
Before you install Android.Auth, Add the required version of Xamarin.Android.Support.CustomTabs (on 5/29/2019 this was 27.0.2.1 to match my Xamarin.Android.Support.v7.AppCompat) to all projects (I'm on 1.6.0.4). Now when you compile it it should not give you a version conflict!