Using shutdown instead of systemctl
The old shutdown commands that we used on SysV systems came with some cool options. We could schedule a shutdown or reboot for some time in the future, cancel a scheduled shutdown, and broadcast a message about an impending shutdown or reboot to all users who were logged into the system. With the systemctl commands, you can't do any of that. Fortunately, the old shutdown options are still with us, in the form of a symbolic link that points to the systemctl executable, as we see here:
donnie@ubuntu20-04:~$ cd /usr/sbin/ donnie@ubuntu20-04:/usr/sbin$ ls -l shutdown lrwxrwxrwx 1 root root 14 May 27 11:16 shutdown -> /bin/systemctl donnie@ubuntu20-04:/usr/sbin$
Even though you can't use the old shutdown options with systemctl, you can use them with the shutdown link that points to systemctl. (Strange, but true.) Now, I realize that you old-timers might know these shutdown commands already, and that's okay. You won't hurt...