Ubuntu 18 - Switching window manager

I'm running Ubuntu 18.04, and want to try the Awesome window manager. I installed it with sudo apt install awesome. How can I switch between GNOME and Awesome?

I found this answer, but I can't see how to "log out, choose the one you want, and log back in." under GNOME.

When on the logon page, next to the "Sign In" button, a little cogwheel should be visible, showing the various options for window manager. I wasn't getting any new options beyond "Ubuntu" and "Ubuntu on Wayland".

Eventually I found out I needed to restart the computer before it gave me the option to log on with Awesome.