On macOS, QLocale::uiLanguages returns a list of languages in order of priority. If this list is set with KLocalizedString::setLanguages, translations are used randomly from the languages in this list, instead of in order. With Plasma or Windows QLocale::uiLanguages only returns one language, so the behaviour is not as apparent.
Hm, Plasma allows to configure multiple languages (including order), but I am not sure if this configuration is used directly, or also passed via QLocale.
Thank you for reporting this issue in KDE software. As it has been a while since this issue was reported, can we please ask you to see if you can reproduce the issue with a recent software version? If you can reproduce the issue, please change the status to "REPORTED" when replying. Thank you!
Yes, this is still relevant. Bugs don't get fixed automagically, on the whole, but need developer attention. And if a developer actually fixes an issue, they will most likely close the relevant bug...