Check Locale, note that within LXQt you can set locales in the GUI which do not (yet) have a translation and will cause error messages. You might want to modify LC_TIME, LC_PAPER, and LC_MEASUREMENT to a different locale than the default locale, and verify the following files are set correctly

/etc/default/locale
/home/user/.config/lxqt/lxqt-config-locale.conf
/home/user/.config/lxqt/session.conf

Lubuntu Manual 19.10