Since the basis of this program is to use the camera, testing the application on a physical device is essential.
In addition, and quite bizarrely, testing on a physical device can actually be faster than testing on an emulator.
In this section, we will cover the basics of what we will need to set this up on our Android device; however, I strongly encourage you to refer to Xamarin's own guide on this: https://docs.microsoft.com/en-gb/xamarin/android/get-started/installation/set-up-device-for-development.
This guide is much more comprehensive and, given that it's updated frequently (whereas this book is not), is an up-to-date guide.
The instructions here relate to Android 8.x (Oreo), but should also work for later versions (at the time of writing, the latest version is 9.x, that is, Pie).