Hi Christian,
the door opener is directly connected to the intercom on the inside. So there is no way to send an opening signal to the system for the electric strike to be triggered. The only way I can think of is to connect the door-opening relay of the Opener (blue, purple) directly to the door-opening switch inside of the intercom. Screw terminal 1 and 2 could be used for doorbell recognition. See Howto connect the Nuki Opener to unknown intercom systems