Wi-Fi connections are not enabled by default on Ubuntu Server. You will need to enable it manually. You can do it during installation (this didn't work for me) and after. Here are steps I needed to do to enable Wi-Fi on my Ubuntu Server. You may need wired connections at first to download some packages or provide them using e.g. USB drive.
I am not and expert in this field so if you find something that can be improved in the Gist let me know :)
In my case I needed to unblock Wi-Fi interfaces. For that I used rfkill
. It was not availalbe out of the box in the server so I needed to download additional package.