Created attachment 137799 [details]
Screenshot of the menu showing the issue with wrong text

SUMMARY
I use kde/okular with a Greek user locale in Archlinux. After v.20.12 (I am not sure which "point" release, as I was waiting for a fix, sorry) 3 base menus' text (File, Tools, Help) were appearing with "Χωρίς κείμενο" (No text) as text, instead of maybe an English translation. 
As it is too basic translation that does not change normally, it must be some accidental "bug".

STEPS TO REPRODUCE
1. Start a KDE session with Greek $LANG/$LC_MESSAGES=el_GR.UTF-8
2. Start okular
3. 

OBSERVED RESULT
Menus that should be Αρχείο/File, Εργαλεία/Tools, Βοήθεια/Help have this text:
"Χωρίς κείμενο"  

EXPECTED RESULT
Menus that should be Αρχείο/File, Εργαλεία/Tools, Βοήθεια/Help have the proper relevant text.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.21.4
KDE Frameworks Version: 5.81.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
I use latte-dock with latte Window Appmenu for the menu system.