If you have Ubuntu 17.10, you may have noticed the switch back to Gnome. However, I personally do not like Gnome 3 and have adapted well to Unity over the years. If you find yourself back in Unity, you may notice that the Gnome login screen (gdm) is still active. It’s actually very simple to switch back. Open up a terminal window and type:
sudo dpkg-reconfigure lightdm
Arrow key down to “lightdm” and then tab to Ok and reboot.