The gnome launcher for xu4 needs the full path /usr/games/bin/u4 placed in the command launcher. It does not work without it. Reproducible: Always Steps to Reproduce: 1.Gnome Applications -> games -> ultima4 2. u4 not found! 3.
You need to be in the games group, env-update as root, log out and log back in. The problem you're having is that /usr/games/bin isn't in your path at the moment.