After upgrade from 17.04 to 17.10 I can only change brightness if I log in to unity desktop and from there adjust brightness setting in system settings.
With Ubuntu 17.10 I have tried following combinations:
Xorg, nvidia & unity: ok
Xorg, nvidia & gnome: not ok
Wayland, nouveau & gnome: not ok
After upgrade from 17.04 to 17.10 I can only change brightness if I log in to unity desktop and from there adjust brightness setting in system settings.
With Ubuntu 17.10 I have tried following combinations:
Xorg, nvidia & unity: ok
Xorg, nvidia & gnome: not ok
Wayland, nouveau & gnome: not ok