I built something similar! https://michael.stapelberg.ch/posts/2021-03-13-smart-interco...

> I bought the cheapest compatible BTicino intercom device (BT 344232 for 32 €) that I could find on eBay, then soldered in 4 wires and added microcontrollers to make it smart. It now connects to my Nuki Opener Smart Intercom IOT device, and to my local MQTT Pub/Sub bus (why not?).