Wine is needed which can be downloaded from https://winehq.org/. Note that the game is 32 bit and most likely needs the 32 bit arch enabled.
For Ubuntu the instructions can be found on https://wiki.winehq.org/Ubuntu including the 32 bit command. At time of writing I am on Ubuntu 18.04 (bionic) with the wine staging branch.
$ wine --version
wine-4.0-rc6 (Staging)
The GoG version of Northland installs and runs without problems.
For multiplayer, directplay is needed which is missing and results in an error message in game. To fix this, install and run winetricks. Select "Select the default wineprefix", then "Install a Windows DLL or component" and tick the "directplay" checkbox.