the solution seems to be two fold with the first one being solved and the second part still open
two separate bug reports have been filed
https://bugs.kde.org/show_bug.cgi?id=499089
and
https://bugs.kde.org/show_bug.cgi?id=499105
first, solving the title issue involved editing the /etc/systemd/sleep.conf to look like this:
[Sleep]
AllowSuspend=yes
AllowHibernation=yes
AllowSuspendThenHibernate=yes
AllowHybridSleep=no
SuspendState=mem disk
HibernateMode=platform shutdown
MemorySleepMode=deep
HibernateDelaySec=60
#SuspendEstimationSec=60min
notice the “freeze” and “standby” strings have been omitted entirely because they are apparently not supported by the firmware.
hybrid sleep is not allowed because my preference would be suspend-then-hibernate, and i will likely increase the delay significantly if i can get it to work from the power management settings
which brings me to the second part… plasma does not seem to be providing the support for systemd that it should since it doesn’t seem to think my machine can hibernate at all even tho it can if i run the systemctl commands in a terminal
plasma will do the suspend part and write everything to RAM but it will not do the hibernate part in spite of turning these things on in sleep.conf, and use of the command line feature in power management has so far been fruitless… i will likely make another post about this part.
UPDATE: the problem seems to be that plasma’s power management suspend feature is different than systemctl suspend
when i use “do nothing” as the option for plasma suspend and add my own script that runs systemctl suspend everything works as expected.
details of the workaround can be found here