That actually works. I think I missed that the console could (only) be reached by 'private wifi ip=192.168.3.1' plus path /console.
I thought http://192.168.3.1/OnionOS/ or http://192.168.178.16/OnionOS/ would show up as the console, or contain a link / button to it.
It is still a bit mysterious why the installer did not properly install the console.(...)