My Dell G5 5090 computer doesn't recognize boot system or recovery tools

I have a problem with a Dell G5 5090 computer. It was working perfectly fine until a few days ago, when it started showing this blue screen at startup.

https://i.imgur.com/qfOGcAN.png

We tried the recovery options, but when we used them, the computer just showed an empty screen and shut down.

https://i.imgur.com/THUy6oi.png

Originally, the computer had a 128GB SSD with the OS and a 1TB HDD for files. But a while back, a new secondary SSD was installed, and the person who installed it says he saw a message he vaguely remembers asking if he wanted to make that the main drive. He thinks the SO was automatically transferred to the new SSD. I don't know if that's possible.

I tried to see if I could find out anything with a USB stick running Linux Ubuntu, but the system says it can't recognize the SSD because it's in RST mode.

These are the drives that appear to boot the system.

https://i.imgur.com/xY32rmm.png

What steps should I take to diagnose the source of the error? I've read that it could be due to a failing SSD, overheating, or any other faulty component, such as the graphics card. For the latter, is it enough to remove the graphics card and test whether the SO boots normally?

Thanks in advance for any help!