Allegedly, on or about 05 March 2016, Timothy Murphy sent:
So one has to start knights, and then choose gnuchess as "computer engine". This strikes me as slightly weird. And what is the option "gnuchess --xboard" meant to do? (It does nothing.) I would have thought an option "gnuchess --knights" (or else a config file .gnuchess where you can specify "knights") would be the rational way to start gnuchess using the knights board.
Are you only starting things through the CLI?
I don't play chess, so I don't install it. But I did for my mother, years ago, and there was a menu item to play chess that just started the whole thing in one go.
So, either see if you can start it that way, or have a look at what command line it used in the menu config.