Not sure if this will be the solution for you, but I also had some issues with my locale(s) coming from Manjaro.
Apart enabling the locale, making sure I selected a “UTF-8” one(s) and generating it with sudo locale-gen, I also had to install the hunspell packages for the needed languages, as the Hyphenation packages (hyphen-en, hyphen-fr, etc…) for the selected locales to stop the Warning/Messages I also got in LibreOffice about a wrong language configuration and missing files.
Also, after having generate the locale, don’t forget to reboot or to run:
unset LANG
source /etc/profile.d/locale.sh