Changing nouveau.runpm=0 to nouveau.runpm=-1 in /etc/default/grub, and then running update-grub, fixed the issue. Back to 6W. Dell XPS 9550.
Changing nouveau.runpm=0 to nouveau.runpm=-1 in /etc/default/grub, and then running update-grub, fixed the issue. Back to 6W. Dell XPS 9550.