So first of all thank you community for the help.
I was able to get the simplified setup up and running for the time being.
I was able to push up the intercom and separate it from the metal bracket.
Then I had to remove a plastic cover that protects the contacts. Then you can simply pull out the clamps, they are only plugged into the intercom and you can then simply work with the (short) cables.
This is how the intercom looks like, after unplugging the clamps attached with wires:
Left side of bus is + (Bus+) and the right is - (Bus-)
I took the simple setup from this (german) pdf on page 6: https://nuki.io/wp-content/uploads/2021/04/How-to-guide-Nuki-Opener_DE.pdf
For ENG, you can download a similar PDF here: Howto connect the Nuki Opener to unknown intercom systems and go on page 8.
Be sure to use “Bus (Bticino)”.
Then I simply connected the wires according to the simple setup, without orange. So red and black only.
They also actually fitted with the existing wiring coloring.
Note during the setup process, you must ring the bell, etc.
I always had some odd Bluetooth connection issue (despite being next to it and connected)
The solution was to go outside and do everything over LTE (+ swearing about Vodafone about bad LTE coverage in Germany…) - but of course this works only if you have the bridge / pro and everything is connected already.
This is how the mess looks at the moment:
I try the advanced setup tomorrow, if I find a solution I’ll post / update. But I guess as other have failed, I’ll probably too. So there is no ring suppression atm.