So, I tried to install Ubuntu Server 16.04.1 LTS while the machine was not plugged into the network, and also did not bother to connect to the WiFi network during the installation from the CD either…
Rusty from last Linux use (circa 2008), I was totally stuck thereafter – no network and no way to add anything else (through the network, because, you know, no network)… Fortunately, SSHd was selected during the installation – so all I had to do was to get the network up, then I could try and do every other thing remotely (well, that is the theory)…
Just in case you really do not have an Internet connection (say, the Ubuntu distribution does not have your NIC drivers), you can then try any of the “offline” methods described here.
Documented, as follows, is my journey to “get unstuck” and continue the set-up…