I have set the compose key correctly by typing
setxkbmap -option compose:rwin in XFCE, but before that I just flipped a switch in Gnome 3. Meaning that desktop environment has different ways of storing this configuration.
To mitigate this in part I'm using iBus, which is okey, but sadly doesn't manage at all the compose key (or at least there isn't documentation that it does) which is managed by the XKB option variables, so I need a way to set this for all desktop environments yet it won't get overridden. Is there such nifty configuration file I can use?
Modifying anything under
/etc/default/keyboard) is a no-go, since each user should be able to use the keyboard as they like.