Comment 8 for bug 1713020

Just to clarify my comment.
If you do not want to see the custom "Ubuntu" session with Gnome extensions that cannot be disabled, you can do the following:

1. from terminal, install gnome session: sudo apt-get install gnome-session gnome-session-wayland
2. logout.
3. on login, click the gear icon, select Gnome instead of Ubuntu.
4. Done, you can now enjoy Ubuntu with vanilla Gnome session.

Couple of notes:

- I agree with comments by Joseph Jasson. Having said that, I understand how Canonical is trying to help its user base with a smooth transition, and I appreciate the effort. If "Ubuntu" session's extensions cannot be tweaked it would be great if those few extensions could have their on/off button greyed out or removed, just for clarity.

- Ubuntu-Gnome is no more as far as I understand, so Ubuntu 17.10 will have to serve both Unity and Gnome fans. With this in mind, I believe it would be great if gnome-session gnome-session-wayland could be installed by default. This could help users switch to the desktop environment they prefer.

I hope this helps
Mauro