libreoffice-kde5 file dialog doesn't add automatically the file extension which are important for.docx .xlsx, otherwise the system recognize them as zip.
When removing that package and letting only libreoffice-gtk, extension are added automatically. But we loose, the qt filepicker.
I'm not sure if this problem ahappens only to us or it happens to kubuntu to. I have bugs filed in libreoffice:
and ubuntu launchapd:
test in kubuntu/kde is appreciated