@mpthompson
Welcome to the HP Forums,
We'll be with you until it's all sorted.
I've reviewed your in-depth analysis and I must say, it's quite impressive the way you've written all the details on here,
That said, I recommend you get back to the OEM as you may be right while you've said that the issue occurred due to a missing software or driver, possibly not detected by the HP Support Assistant either while using the version of windows in use.
If you haven't used the HP Recovery manager to revert back to the OEM: Microsoft Windows 10 Home High End (64-bit)
I suggest you order one using this link: Click here for details.
And use the same to resolve this issue.
Also, about Speedfan and HWMonitor, HP doesn't recommend or support using such 3rd party applications, as an alternative you may use the HP Omen controller to complete similar tasks.
If you feel I was helpful, simply click on Accept as Solution to help the community grow,
That said, I will have someone follow-up on this to ensure you've been helped,
Just in case you don't get back to us within 24 - 48 hrs, and have a good day, ahead.
Riddle_Decipher
I am an HP Employee