I would probably try running
strace okular | grep openat
to see all the files it's trying to read and see if any aren't managed by your package manager and move those.
But the latest reply by felixernst in the kde discuss also looks helpful.
KDE is an international technology team creating user-friendly free and open source software for desktop and portable computing. KDE’s software runs on GNU/Linux, BSD and other operating systems, including Windows.
If you encounter a bug, proceed to https://bugs.kde.org, check whether it has been reported.
If it hasn't, report it yourself.
PLEASE THINK CAREFULLY BEFORE POSTING HERE.
Developers do not look for reports on social media, so they will not see it and all it does is clutter up the feed.
I would probably try running
strace okular | grep openat
to see all the files it's trying to read and see if any aren't managed by your package manager and move those.
But the latest reply by felixernst in the kde discuss also looks helpful.