This is not the only possibility, I guess.
Other changes might have happened on the system by any package, application, utility or manually by the admin to break this feature.
Not that it is not by an updated package, but I added for clarity.
If you really want to pinpoint the issue, you may install Garuda (on a new spare drive?) on the same computer, check that sleep is working OOTB, reboot and upgrade your system.
After next reboot, you should have your answer… 
I still suggest trying Arcwiki for solutions.