I installed Antergos with GNOME3 a week ago and so far, everything worked flawlessly. Before, I used Ubuntu for quite a long time (>5jrs).
My system language is German, and in all applications so far, this was also respected. But now I installed Okular (a KDE app using Qt5 I suppose?) and it will only be displayed in some Arabic language:
I also tried to open some other qt application (in the screenshot the configuration tool of qt5) and experienced the same behavior. In contrast, all other applications using GNOME3 work as expected.
I tried to switch the system language to English but nothing happened. I also tried everything mentioned in https://wiki.archlinux.org/index.php/Locale with no effect. Starting Okular via the terminal with setting environment variables like
LANG=de okular also had no effect (I tried LANG, LANGUAGE and LANG_ALL).
Any ideas how to fix this are highly appreciated.