Ask HN: How do I allow my deaf friend to hear the door?

My friend is deaf, which affects his ability to hear people at the door. He has a doorbell which causes his phone to vibrate, alerting him. However, it seems that an overwhelming number of delivery people / visitors knock on the door, instead of using the doorbell.

Is there some similar technology that instead uses cameras that's privacy protecting? I've heard terrible things about ring on this site, but I guess "that sort of thing".