Changing Keyboard Language
Although I've added several languages in the "Layouts" tab of the "Keyboard preferences", I do not see the language icon in the panel tray, nor can I switch between languages.
Does the usual keyboard shortcut Super+Space work (Super is the Windows key on most keyboards)? If so, the problem must be that some "indicator applet" (or whatever it is called) is missing from your panel.
Since you do not specify it, I imagine that, unlike me, you use Trisquel's default desktop environment, MATE. Somebody using that same environment would be of better help than me to list the steps to add the proper element to the panel.
I am a translator!
Add the "notification area" applet to a mate panel. This is not the "notification" applet that shows battery, wifi, sound, etc, it is another one. On my desktop, the "notification area" applet only shows the language and the Gajim icon.
How did I find? I tried everything.
I use MATE because it is the default, it has a rather easy interface, it seems good enough so that I don't feel like spending time to setup something else. However, the documentation is almost non-existent.
Note that the applet names I am giving might not be the ones you see because my setup is not in English so I am trying to guess the English names from another language.