So, I have bought a mintBox to use as a home server. It took me a while to figure out that you cannot login over ssh using the credentials printed in the manual that comes with the device.
But the password works, surprisingly, for ‘root’ to login over ssh. So, connect your mintBox via an ethernet cable to a DHCP-enabled router, check for the IP and you are good to go to set it up without a screen.
It’s probably a good idea to disallow root logins via ssh, as soon as you have set up a proper user.
Just putting this here to help other people with the same problem as the solution is not to be found via Google yet.