As first requested here, UniFi Protect Application 4.0.21 added the ability to display custom animations on Doorbell Pro devices. It’s seems to be fully supported in the UniFi Protect application, but not in the Home Assistant UniFi Protect integration. It seems the proper way to do this is to add an image entity that can be updated manually and/or via automations.
I would like to second this request. I have my G4 Doorbell Pro integrated with my Level Lock Bolt and I am also sending a custom ring through the speaker using HA. I current have two MP3’s configured - one for Nov 1-Dec 31 (Christmas Season) and the other which plays at all other times when the doorbell is pressed. I was surprised to learn I couldn’t send a video in the same automation since it’s not currently supported. I handed both GIFs loaded in through Unify and have to manually activate one or the other in Unify.