I'd like to try the Polish Colemak layout. It's built into xkb:
/usr/share/X11/xkb/rules $ grep -ri 'Polish (Colemak)' * base.extras.xml: <description>Polish (Colemak)</description> evdev.extras.xml: <description>Polish (Colemak)</description>
Unfortunately, when trying to add the layout through the Keyboard app ( Layouts > + > write "colemak") the desired layout is not visible. How can I fix it?
I'm using Linux Mint 17.2 Cinnamon