Thank you both for the prompt reply, I'm waiting the cables and will order the proposed one for debug
I was supposing that the images that I tried booted since the LED was blinking differently that when the Rock is only powered that time the LED is only on.
When try the Radxa OS the LED was blinking once, so I supposed it is booted, I was also able to "see" the rock S0 with the RKDev tool.
After looking around more I found what I needed and that is the image of the HA for Rock S0 on Armbian 🤩. Once started the Rock with the HA image the LED was blinking 2 times so I supposed that the Rock boot-up correctly. But that's all, no COM port no IP on LAN visible,...