digiKam 5.6.0 on Ubuntu 17.04 (Unity), menu items don't render. Installed via PPA at https://launchpad.net/~philip5/+archive/ubuntu/extra. Took the desktop file "org.kde.digikam.desktop" and added "env XDG_CURRENT_DESKTOP=Unity" in the Exec section, making it: "Exec=env XDG_CURRENT_DESKTOP=Unity digikam -qwindowtitle %c". Now menu entries work. This tip from http://www.webupd8.org/2017/03/fix-dropbox-indicator-menu-not-working.html Sorry if this bug is in the wrong place.
Please report this packaging problem to Ubuntu team as DOWNSTREAM