I've been using Ubuntu Gnome for around 5 years, and recently upgraded to 17.10. With this release, I've noticed a problem I cannot seem to resolve.
Under the "Power" settings is an option to "Blank Screen" after a specified interval. Since I've updated to 17.10, this value is ignored; the screen never blanks.
I am using GDM for my display manager, with Wayland as the display server. I do not have gnome-screensaver installed.
I can use
<Super>L to lock the screen, and this works, but I'd prefer the autoblanking behavior.
(Interestingly, on a laptop on which I did a fresh install of Ubuntu 17.10, this seems to work fine, which indicates to me it is potentially an upgrade issue.)