Thanks for the kudos, I think we are getting closer to the culprit!
What you found is exactly what I was suspecting of something additional needing to be added but I just didn’t know enough to say anything substantial. I did create that udev rule and nothing changed. Though that post got me thinking, I noticed that OSMC does not have a /sys/class/thermal/cooling_device0 symlink or base location at /sys/devices/virtual/thermal/cooling_device0. I was operating under the incorrect assumption that thermal_zone0 was some sort of artifact with a different name but looking at the Raspberry Pi OS system both exist:
ls -l /sys/class/thermal/
total 0
lrwxrwxrwx 1 root root 0 Jun 9 15:18 cooling_device0 -> ../../devices/virtual/thermal/cooling_device0
lrwxrwxrwx 1 root root 0 Jun 9 15:18 thermal_zone0 -> ../../devices/virtual/thermal/thermal_zone0
And as that article alluded to, I checked the types of both and they are different:
tail /sys/class/thermal/cooling_device0/type /sys/class/thermal/thermal_zone0/type
==> /sys/class/thermal/cooling_device0/type <==
rpi-poe-fan
==> /sys/class/thermal/thermal_zone0/type <==
cpu-thermal
For comparison’s sake OSMC’s /sys/class/thermal looks like this
ls -l /sys/devices/virtual/thermal/
total 0
drwxr-xr-x 3 root root 0 Jun 9 08:37 thermal_zone0
And with the expected type of cpu-thermal
cat /sys/devices/virtual/thermal/thermal_zone0/type
cpu-thermal
So I think the culprit is the cooling_device0 device missing on OSMC installs. Now solving that is out of my realm but if there is any material I can review that could point me in the right direction, I am willing to test out my theory.