Remove ubuntu-desktop
Solution 1:
You can remove Unity as answered on our forum by Dennis:
sudo apt-get autoremove --purge unity unity-common unity-services unity-lens-\* unity-scope-\* unity-webapps-\* gnome-control-center-unity hud libunity-core-6\* libunity-misc4 libunity-webapps\* appmenu-gtk appmenu-gtk3 appmenu-qt\* overlay-scrollbar\* activity-log-manager-control-center firefox-globalmenu thunderbird-globalmenu libufe-xidgetter0 xul-ext-unity xul-ext-webaccounts webaccounts-extension-common xul-ext-websites-integration gnome-control-center gnome-session