Comment by FlorinSays

I had the same problem and I've searched for ready made solutions for over an year before I found a guy that reverse-engineers and builds ready-made boards to install in my intercom for less than 30 euro.

I'm unsure if I should post the link or not as it's specific to Romania, but I love how janky the buids are: https://www.olx.ro/d/oferta/automatizare-interfon-electra-cu...