I've installed the latest 17.10 Ubuntu and then used
sudo apt install gnome-session
to get rid of Ubuntu's modifications, as described here.
Although I prefer to have a vanilla GNOME experience, Ubuntu's new GNOME-Shell theme is very appealing. Unfortunately, I can't find this theme in GNOME Tweaks. The only GNOME-Shell theme that is present there is GNOME's default one.
Does somebody know a convenient way to install Ubuntu's new GNOME-Shell theme?