I’m losing my mind at these Ionic 4 native plugins. They seem to almost never to work. My newest hell is Firebase Authentication plugin (https://ionicframework.com/docs/native/firebase-authentication). When I try to run my project on android device, it gives me error that the cordova-plugin-firebase-authentication plugin is missing. I have removed / installed it several times and also removed / added platform several times with no joy. Same error every time. ARRRRRGH!
Switching back to angularfire 2 
Keep your natives… I don’t have time to wrestle with this s**t