Hmmm ....

Been there and done that.
Quite a few times actually.

Assuming that because it was a [Sun/HP/IBM/Dell/Sony/whatever] unit, it could not be what I suspected from the start.
25+ years later, I know better.

Glad you got it worked out.  8^D

Best,

A.

I installed Crucial Ballistix memory (it has a thin aluminum strip covering the chips to serve as a heatsink). Maybe it'll keep those temps lower. It is a matched set of 8 GB each, so performance can only improve.

I drilled a few holes in the bottom case under the NVMe SSD. It can only improve the airflow, especially considering that it's located at the far corner of the laptop with no otherwise ventilation.

But the biggest bang for the buck was with the processor. My old HP laptop has a copper heatsink and bar, but this new one has a thin aluminum one. Damn those beancounters! When I removed the heatsink, I found a glob of thermal paste. It wasn't hard or crusty, just applied far too thick. When I applied a thin coating of Noctua thermal paste, the temps dropped around 25 degrees!

It was a hardware problem all along.

Absolutely. The processor temps are much higher than they should be. Looking at the HP manual, the same heatsink bar is used for both processor and GPU, so it's a two-fer.

advertised it as refurbished, whatever that means

It's a meaningless marketing term with no legal basis. s/refurbished/cleaned/g.

Yeah, this is a funny laptop. I bought it from Newegg, which advertised it as refurbished, whatever that means. I really think it is gray-market from Asia. It has a truly matte screen, which for me is a hard requirement, as well as an NVMe SSD and AMD Ryzen 5 processor. The vents are pretty much a joke, really tiny holes that could not possible transfer much air. I'm going to drill-out the outer ring of vent holes to improve the airflow. When I do that, I'll make sure the fan is not obstructed.

Those two statements appear to be contradictory

Mentalist

^ This.

There is plenty of malware floating about that will infect a Linux system directly but ClamAV won't catch any of it.

Thanks to everyone for their assistance.

@GlennW

I updated the BIOS to the most recent one as soon as I acquired the laptop. I had to do it immediately because I was planning on replacing the low-capacity "value" SSD it arrived with (it had Windows installed and HP's BIOS update only works with Windows). And I have never used torrents, but it's good to know that rebooting after using them is recommended practice.

Correction...
I said the wrong thing about my fans, it's not that they switch off, it's that they switch to full ON, and the noise alerts me, then I feel the excessive heat with my hand. I have 2 fans on the Noctua cpu heatsink, and a psw internal fan, and 4 case fans, when they all switch to full speed it's very obvious/noticable.
Regards, Glenn

Forgot to mention the gpu fan, which hardly ever comes on.

Well, that's curious. On a lark, I uninstalled Britty because I'm not blind, uninstalled Clamav and Clamtk because antivirus often uses lots of processor resources, and Gnome Software which I didn't remember installing (but I'm sure I did). The fan is now quiet. It appears that Clam was the problem all along, which is highly ironic.

That's been my experience with clam. Not sure if it's even useful on a desktop installation - isn't it just checking windows virus definitions? It seems like it's mainly for things like email servers.

UPDATE: I spoke way too soon. When I wrote the above, no browser was running. Now that I started using browsers again, the fan is once again running. Time to take the back cover off.

I updated the BIOS to the most recent one as soon as I acquired the laptop. I had to do it immediately because I was planning on replacing the low-capacity "value" SSD it arrived with (it had Windows installed and HP's BIOS update only works with Windows). And I have never used torrents, but it's good to know that rebooting after using them is recommended practice.

On the temperature front, the NVMe SSD has reached 84 c as per Psensor, which is disappointing given that it's a Samsung Pro with a piece of aluminum Samsung laughingly calls a heatsink. I am beginning to think airflow is an issue, something I will investigate when I open the back. Maybe it's time to drill a few holes in the back. ;-)

And I think it's true what "andyprough" says about torrents...

I usually have to reboot after visiting torrent sites to stop my PC temps from running away when the fans turn off.

But not just downloading Torrents like Devuan iso's.

For your sake, I hope it's just a bios update. :-) all the best.

p.s.  I use Lynis, chkrootkit and rkhunter and clamav daily and they don't show anything in particular. Lynis helps with hardening tips, but I have found there is a limit to how "hard" and still being able to use my computer. Cheers!