Need help with booting OS on X220 (it won't boot)

[replica9906]

I am trying to boot my X220 into Debian through SSD, and the SSD is recognised and properly plugged in — I've made sure of that many times, but the laptop won't boot. This is through the standard HDD slot. Previously, it booted Windows 11 Pro through an SSD without problems. The OS on this SSD boots on T430. I also tried using a different disk which I recently cloned from, so it's almost the exact same copy but on a different device, and the same problems occurred.

I also tried choosing it as the temporary startup device. It is first in the boot order.

The UEFI picture with two dialogues is what happens when I force it to boot through this SSD. Repeated attempts even through this UI lead to the same. The other two pics are messages when the computer boots with the SSD as the first and only choice to boot from.

Edit: Turned out I had the PXE-E61: Media Test Failure, Check Cable' Error which happens when the computer tries to boot over a network instead of local drive, but fixing that still leads to the same blue boot menu screen: https://www.idrive.com/idrive/sh/sh?k=p4g3z8m9k0.

I also made sure to verify all the other boot settings and made sure UEFI/Legacy boot modes are not a problem. Compared settings with T430 which correctly boots from the disk.

Any clues highly appreciated...