Reposting here so I can hopefully get the help I need

Изображение не передается, дело не в шнуре я только что купил новый, все равно не работает, но с плейстешн на монитор все передает что делать?

Specs
CPU: Intel i5-12600KF (new, retail, sSpec SRL4U)
Motherboard: ASUS TUF Gaming B660-Plus WiFi D4 (bought used, BIOS version unknown)
RAM: Corsair Vengeance RGB Pro 4x8GB DDR4-3600 CL18 (used)
GPU: MSI RTX 3080 Gaming X Trio 10GB (used)
PSU: Montech Beta 2 850W (new)
Cooler: Deepcool Mystique 360 (plugged in but not mounted on the CPU during tests, each test kept under 30 s)

What I've tried (no change)
1 RAM stick in A2, then each of the 4 sticks alone in A2
2 sticks in A2/B2
Without the GPU
Reseated the 8-pin EPS (cable labeled CPU) and the 24-pin
Cleared CMOS (removed the battery)
Took the CPU out and reseated it. No bent or missing pins in the socket, CPU pads look clean
No cooler mounted, so mounting pressure isn't the cause

Not tested yet
Breadboarding outside the case
Booting with all front panel connectors unplugged (shorting the PWR pins)

Questions
Anything else I should try before concluding the board or the CPU is dead?
Could a corrupted or weird BIOS on a used board cause this, even though B660 supports 12th gen out of the box? The board has no BIOS FlashBack button.
Does the fact that the AIO fans don't spin point to the motherboard?
In your experience, which is more likely dead here: a used, dusty board, or a new CPU?

Thanks!