Builders Door

Get it on F-Droid
Add to F-Droid: https://builders.colinknapp.com/fdroid/repo
Direct APK download

Receive front door calls with Builders Door.

Download Android app

No sign-in is needed to download or install. Open the app on your tablet, choose Scan administrator QR, then scan the one-use QR shown by an administrator on their computer.

Android installation instructions