I have recently updated to Mac OS High Sierra (10.13.3) and installed LMS 7.9.1 but I am experiencing issues with WOL. My SB devices can wake up my iMac from sleep, but after a minute or so Mac OS goes back into "maintenance sleep" and streaming is interrupted. However if I wake the iMac manually e.g. from the keyboard, LMS seems to keep it awake, presumably via the Prevent System Standby plugin? So it seems the plugin works when the Mac wakes "normally" but not when it experiences a "dark wake"

My system power settings are:

standby 1
Sleep On Power Button 1
womp 1
halfdim 1
hibernatefile /var/vm/sleepimage
powernap 1
gpuswitch 2
autorestart 0
networkoversleep 0
disksleep 0
sleep 0 (sleep prevented by caffeinate)
autopoweroffdelay 28800
hibernatemode 0
autopoweroff 0
ttyskeepawake 1
displaysleep 15
standbydelay 10800