Comment 4 for bug 1605571

Since you mentioned Lubuntu, they have this in the desktop seed:

$ apt-cache depends lubuntu-desktop | grep fcitx
  Depends: fcitx
  Depends: fcitx-config-gtk2
  Depends: fcitx-frontend-gtk2
  Depends: fcitx-ui-classic

Without having tested, I suspect that something like that is what's needed to actually be able to use Fcitx easily in a live session.