For some European intercoms, there is Doorman [0]. Their authors reversed engineered the protocol used by Koch and built an ESP32 + Home Assistant solution that works quite nicely (including board). The "party mode" [1] was a life saver for me when doing events on the rooftop.

[0] https://doorman.azon.ai/ [1] https://doorman.azon.ai/guide/features/ring-to-open