David, maybe worth looking at, too, is other options to shutdown (or reboot), at Terminal, as your article says.
For my part, I find it easy to use the runlevels, numbered init 0 (zero) through init 6. The two that are relevant are
init 0 for shutdown
and
init 6 for reboot
These can be used in any Debian-based Distro, and for the most part without needing sudo.
Debian itself, and related distros such as the MX-series, need to be prefaced with sudo. You’ll soon find out which needs what.
Where init is used followed by a runlevel number, that is mostly interchangeable with
telinit
and both go back to sysvinit as a service manager. Nowadays of course more than not distros use systemd as a service manager, but for many of them they have a Legacy sysvinit-systemd component included and so the commands are usable.
Where that Legacy feature is not built in, systemd has replaced runlevels with targets and the numerals 0 – 6 are replaced with names ending in
.target
I can show the readers these options as they apply to other Families, which in my stable of Distros include
Fedora and Mageia (RPM)
openSUSE (using Gecko Linux) (other RPM)
Calculate Linux (Gentoo)
and then of course there is the Arch family (represented by Manjaro, Arcolinux and EndeavourOS).
Cheers
Wizard