Section 17 was still labelled "XFCE + VNC" while the step it runs installs
ubuntu-desktop and is guarded on it, so the heading described a setup the
script had already stopped producing.
Also spell out why setup-desktop.sh disables lightdm: it is not a display
manager this script ever installs, it is residue on hosts set up by an earlier
version that did install XFCE, and left enabled it beats GDM to the seat.
Comments and one echo string; no behaviour change.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>