Looking for a suitable doorbell for CAT 7 cable

Is the CAT cable not in an empty conduit? If yes, wouldn't an additional cable for the 24V supply fit through it?

We got the Acuvox R26 back then. It runs via PoE on the LAN. The doorbell comes through the landline phone, the video signal is also played there, just like the intercom system.

Currently costs 195 euros on Amazon. You just have to search for Acuvox IP DoorbSIap Intercom.

Isn't the CAT cable in an empty conduit? If yes, wouldn't an additional cable for the 24V power supply fit through?

Good idea! But unfortunately no empty conduit available :-(

But that is not DIN-compliant ...

Do all cables in a house have to be laid in empty conduits?

Not all cables, but according to DIN 18015 all cables "for reception and distribution systems" as well as "telecommunication systems," which includes network cables.