OK, so, in my tests, no problem with Cachy Nord. That was using my app, tomboy-ng. You saw the screen shot. So, its either your test app, some residual config you have changed, libqt5pas or bad karma. You might like to consider installing Virtual Box and do you experimenting in a VM, you feel a lot more confident ....
'yay' ? is that a command ? A package installer ? Where do the packages come from ? Or is it, Yay, as in "Yay that I walk through the Valley of Death, I fear no segfault ...." ?
My guess is that the libqt5pas you found is OK, using release Lazarus, even a quite old one should work.
But if you want to, and are feeling a bit brave, you could download the tar.gz file from the link I put in my previous message and put its content in place of the one you currently have in /usr/lib. I am a bit unsure where you got the existing one from.
I'd take a screen to shot of how "ls -l" sees then now, move but keep a copy of the existing binary and delete the two or three symlinks. Put the new binary in the same place and add the symlinks to it. (Lazarus uses one of the symlinks so you can probably leave the old binary where it is and just change the symlinks, but it is surer if we rename it). Careful to change nothing except libQt5Pas and don't tell anyone I told you to do it this way.
Otherwise, i suggest you make a new test app, try that, maybe I make you a new test app to try, just to be sure.
Davo
Edit - as forum will not allow uploads of binary size attachments, I have put a test binary (and its source) in the bleeding edge libqt5pas repo.
https://github.com/davidbannon/libqt5pas/releases/download/v1.2.12/testQt.tar.gzUsual warnings apply.
Davo