"There are drop-in directories available in all of the configuration directories, but the most popular drop-in location is in /etc/systemd/system/.d/."
I could not locate that directory on my system.
The directory "/etc/systemd/system" should be there. Additional directories may be available under that directory like "/etc/systemd/system/someservice.d". The directories under "/etc/systemd/system/" are not created by default. A full description of the directories is available from " man 5 systemd-system.conf"
Thank you for noticing, we will correct the typo.