Under Preferences > General, there is an option to set your External Editor. Use the Other command line to launch gimp and set your language. Something like this:
LANG=hu gimp
https://discuss.pixls.us/t/rawtherapee-5-3-524-and-gimp-2-9-9-on-ubuntu…
Értelemszerűen a locale -a elárulja, hogy mik elérhetők.