Comment # 7 on bug 1150463 from Wolfgang Bauer

(In reply to Wolfgang Bauer from comment #6)
> Then Leap 15.1 should be affected too though...
Yes, it does indeed affect 15.1 as well.

It's apparently caused by this change in LibreOffice 6.2.5.2, which changes
LibreOffice to use gtk3 on Plasma/Wayland:
https://gerrit.libreoffice.org/plugins/gitiles/core/+/1124e98e935cec42c51f25f1fc713285b1044d07^!

Reassigning to LibreOffice, this has nothing to do with "KDE Applications"...