Can't switch/use input methods

[Caleb Herbert]

When I'm using Guix-installed apps, I can't use my input method switcher
Fcitx.  I've tried changing the input method with both the mouse and the
keyboard, in HexChat and Mumble.

Fcitx was installed with the system's package manager because it
interacts with some system services and the Guix version gets confused
and makes it so I can't even type the Latin character "a".  Also, Guix
doesn't have Fcitx Mozc for Japanese.

I would like to use Fcitx for everything.  On other systems, it has
allowed me to type any language or script that comes to mind (except
emoji, Yiddish, International Phonetic Alphabet, Shavian, runes and
Egyptian hieroglyphs, unfortunately.)