B650 Steel Legend WiFi no POST suddenly

Yeah, I don't see any red flags.
Chalk one up for bad luck, I guess.

Hi,

The full list of components is at the bottom of my OP.

The technician spent an ample amount of time diagnosing everything in the PC. He did insert one of his spare CPUs into the MOBO as well, was reluctant to do it the other way round (it's a small shop, though with houndreds of amazing reviews). He mentioned that there have been lots of people coming in with dead AM5 CPUs in recent months.

I've decided to go with B850 tomahawk max wifi this time, due to pretty much the same price and amazing reviews.

The PSU seems pretty good, though there's always a chance...Mind that the computer was not under stress when it happened.
Can I even RMA the PSU only on the basis of both components simultaneous failure?

Your case is unusual.
1) Both the motherboard & the CPU died. Normally, the motherboard isn't killed, unless there is a physical burn type failure.
2) The motherboard failed with just the CPU diagnostic light. The more common is with both the CPU and the DRAM diagnostic lights.
3) You had a non-X3D 7000-series CPU.

One question, though. How did the local technician confirm that the motherboard was dead? If he was afraid to test the CPU in another motherboard, in the fear that it could damage a perfectly good motherboard, he wouldn't have put a perfectly good CPU onto the motherboard to test it.

But regardless, assuming all three of the above assumptions are true, then I would highly recommend you replace the power supply. Other than lightning / electrical surge type events, the most common cause of motherboard+CPU failure is the power supply.

At minimum, tell us what brand/model of power supply you have, along with other components in the build. I'm just curious if the power supply was running near its limits or not.

No one knows for sure and none of the manufacturers are talking. Personally, that
makes me suspect AMD. If all the other brands were wagging fingers at ASRock or
another brand that would be different but they are keeping quiet too.

Blame aside, ASRock did release this statement a few days back, along with BIOS
updates intended to address concerns:
https://www.asrock.com.tw/news/index.asp?iD=5744

In spite of all the publicity and attention being drawn to this issue it is still
an exceedingly rare occurrence. To put it in perspective, there were more dead
CPUs caused by intel's mess up with 13th and 14th gen microcode. These things
happen. It's better for it to be a known issue that is receiving support and RMAs
than for it to be completely isolated and potentially fall outside warranty etc.

As to sticking with the platform, that is entirely up to you. Personally, I
would see how it goes with the replacements and the new BIOS updates. If something
goes sideways again then swap out the 9000 series with a 7000 series CPU and be
done with it. As in, get the replacement CPU (RMA) then sell it and pick up a
7000 series equivalent. In all likelihood your system will be fine now. It would
seem AMD has been working with all it's board partners to get the the bottom of
this issue.

Bare in mind, all AM5 boards available gave no issue with 7000 series CPUs.

As for this being an ASRock issue, no, it isn't limited to ASRock, other manufacturers
are experiencing failures too, it wouldn't surprise me if they all were. The
reason ASRock has gotten more attention is because more users reported burned
CPUs on an easily accessible redit group. Reports of similar issues from other
brands were not so neatly collected in one place. I believe there have been more
reports of failed CPUs on ASRock boards, I am not trying to say otherwise, but
not by anywhere near the margins the media is trying to claim.

To put your mind at ease, even if you run into problems again, they will be addressed
again. I doubt that will be the case however, you should be fine with the new
updates.

Just sit back, enjoy your build and keep an eye on the ASRock news page for updates
etc.

Good luck and let us know how it goes when you get the replacements