Since we are still waiting for a solution for the missing “ring-to-open” function for the ABB or Busch Jaeger products, I came up with a workaround which works perfectly for my usecase. I even prefer it to the “ring-to-open” function, because it doesn’t unnecessarily scare up anybody at home.
There is one requirement: your entrance has to be within reach of Zigbee, since the actual remote signal is initiated by a hue dimmer switch.
This is what I did: I added homekit support for the opener with a homebridge plugin, that runs on a docker container on my synology (you can also use a rasberry pi or sth similar). Then I programmed the hue dimmer via the homekit app with an opening signal for every button. Then I taped the dimmer switch in my mailbox. I can easily reach it, but nobody else will ever know it is there, and it only opens the door to the building, not to my appartement. Im totally fine with this solution, but of course everybody has to make up his own mind about possible security issues.