I'm using Ubuntu 17.10 and the new default GNOME theme is not installed.
Is there an option to be set?
I ran this command:
sudo apt-get update && sudo apt-get upgrade && sudo apt-get dist-upgrade && do-release-upgrade
My system still has the old unity theme, and I want the new one.
Solved
After the installation you should be able to select the GNOME desktop on the login screen.