Found a better fix, cause with the other one I had issues with the launcher showing a second icon when the application was launched. You basically have to add ‘env XDG_CURRENT_DESKTOP=Unity’ after the ‘Exec=’ in every .desktop file, then the Libre Office just works like in 16.04 and the Libre Office menu button is gone too. You also have to do this with Java Apps like JDownloader after enabling Jayatana so the global menu gets loaded properly.
The line for Libre Office Writer looks like this then:
Exec=env XDG_CURRENT_DESKTOP=Unity libreoffice --writer %U
Don’t edit the .desktop entries in /usr/share/applications, first copy them to ./local/share/applications and edit those.
Can we somehow ship modified .desktop files for Libre Office if someone is installing ubuntu-unity-desktop?