I’ve been adventurous enough to upgrade my iMac to Ubuntu 17.10 Artful Aardvark. That’s the one that features Wayland instead of X Window and Gnome Shell instead of Unity.
The upgrade process proved to be a big challenge and took almost a week, since a regular system update resulted in a black screen. It required a complete OS reinstall from scratch in order to get it working, and then a few more weeks to have it configured my way. The thing is, settings in Gnome Shell are sometimes located at the most bizarre places of Gnome Control Center.