Anyway now I am pretty convinced it is a old BIOS topic, I ordered a AMD Ryzen 3 3200G on Amazon that I will return 5 minutes later after the BIOS is upgraded.
It works, but I lost a year of life plus a kidney.
Removed everything, installed the 3200G. POST finally ok, BIOS 4201 on the effing MB.
Upgraded to 4402.
Swapped back the ebay used 5900X, installed a good known graphics card.
NOTHING LED VGA STUCK ON.
Just because it was on my desk, I swapped the 5900X with the brand new 5950X.
Guess what, now that bastard boots.
Why on earth the boot error VGA LED is on and if I swap the CPU it boots fine? Thanks ASUS to point me in the wrong direction.
I am so wasted I will now keep the 5950X and sell for parts the 5900X at loss.
Currently hammering the 64GB ECC with memtest86, next step Win10 check if everything is recognized okay and the prime95 as final test.
Wish me luck.... I feel like I am painting without eyes.