I’ll take the liberty of digging up this thread from last year again.
We are currently also dealing with the topic of doorbell/intercom system. This topic is completely new territory for us. Our electrician usually installs a system from Doorbird. Since we are already planning a KNX system in the house, operating an "additional system" — meaning the app from this manufacturer — would be redundant for us, or rather, we would prefer to have everything running through one system. Now the question is whether it would make more sense to go for another KNX-compatible system? Doorbird does advertise that it is KNX-capable, but if I understood correctly, only signals, not video and audio, can be transmitted via a BUS cable.
Maybe you can share which video intercom system is integrated into your KNX system and how it has been working so far.
It is important to us to see (and hear) who is at the door, no matter where we currently are, and also be able to talk and possibly open the door from there. So ultimately, an interface on the smartphone. I can hardly imagine having a fixed display somewhere in the house anymore. But maybe you can also offer a different perspective here.