I have upgraded to Ubuntu 22.04d OEM 6.5 kernel. Also installed @Mario_Limonciello PPD PPA.
The upgrade broke the OEM c kernel notification & grub edit script which insisted on sticking with OEM 6.1 rather than 6.5 kernels, but I got through that.
With just these two changes, plus powertop --autotune my power consumption has dropped quite a bit, now baseline in the 4-5 W range. Web surfing has not exceeded 7W so far.
After several hours of use, powertop reports 94% in C3 overall.
Nice work.