What PC hardware diagnostic stress-testing freeware can you recommend?

What PC hardware diagnostic stress-testing freeware can you recommend?

o I have a random hardware related BSOD whose cause is unknown to me
  <https://i.postimg.cc/9Q4m7tfM/bsod01.jpg>
  <https://i.postimg.cc/DyNFnJcK/bsod02.jpg>
  <https://i.postimg.cc/XYnhMnR0/bsod10.jpg>
  <https://i.postimg.cc/T2mHpyG6/bsod13.jpg>
  <https://i.postimg.cc/5t6s1ypD/bsod15.jpg>
  <https://i.postimg.cc/T1X0r9GX/bsod16.jpg>
  <https://i.postimg.cc/8khtTqBk/bsod18.jpg>
  <https://i.postimg.cc/LsjxVzL2/bsod19.jpg>

It could be the motherboard, a daughter card, the HDD mechanics, etc.

I first ran the Windows memory diagnostic freeware to no avail:
 <https://i.postimg.cc/d3xZzxrd/bsod24.jpg>
 <https://i.postimg.cc/VvmczfBP/bsod25.jpg>
 <https://i.postimg.cc/kMc0xdvD/bsod26.jpg>

As per the kind suggestions of "n/a" and others, I ran memtest86 freeware
on that old BIOS desktop in an attempt to identify its hardware faults:
<https://alt.comp.os.windows-10.narkive.com/oL7PTNKu/windows-10-bsod-indicates-a-hardware-problem-but-what-hardware-is-the-problem#post17>

The old BIOS desktop booted a 32GB Memtest86 USB stick to ran overnight, 
finding no errors on 16GB RAM (I stopped it after 5 hours & 6 iterations):
 <https://i.postimg.cc/KY1Yk4WP/memtest02.jpg>

If it's not the RAM, it's something else hardware related (the HDD has been
re-imaged multiple times in its entirety and all extraneous boards and
peripherals have been disconnected).

What other hardware diagnostic stress-testing freeware can you further recommend?
-- 
Usenet is a wonderfully public way to identify freeware of interest.