That was a surprising find. Libreoffice wouldn't start anymore (just some splash screen with a progressbar, then nothing happens).
After some debugging (comparing my normal zsh session where it wouldn't start, with a clean `sudo -u dfaure bash` session where it worked), I found the culprit. I had QT_NO_GLIB=1 in my environment for some reason, and that's what breaks libreoffice...
Posting this in case it helps someone one day ;)