I was able to solve the problem. I flew to South Korea and took my lens to the customer center. In a matter on 5 minutes they updated the software in the lens and it now works flawlessly with my R6 mk ii.
Before that, my provisional solution was to cut out a ring of very thin but sturdy plastic and insert it in my EF-RF converter between it and the Lens. This blocks the contacts so the camera does not even try to communicate and as long as you enable the shoot without lens in the menu, you can use it fine (with no aperture control). To select my aperture, I put the lens on an EF body, select the aperture and detach it with live view enabled. The blades will stay at this aperture until it is connected again to a body with contacts.
