You’re exactly right @gvolt, thank you for the correction. No idea why I did it. I’m not going to go back and change each post, because it loses context for someone following the topic chronologically, so I will just add a link at the end of the two incorrect posts pointing here.
My sincere apologies for my mistake in including the path to the timer file when the timer is started/stopped/enabled … you just use the timer filename. (However, you do still need to use the full path when creating the file with ‘nano’.)
sudo systemctl start /etc/systemd/system/systemd-reboot.timer
sudo systemctl start systemd-reboot.timer
If you followed the original posts (using full path), then you also need to run:
sudo systemctl disable /etc/systemd/system/systemd-reboot.timer
(Don’t forget to enable it again, correctly … sudo systemctl enable systemd-reboot.timer).