I don't mind wiping all data.
I have looked up similar issues but can't really find anyone in my situation. Many answers assume I can enter grub menu, others assume you can access the live USB, and others assume you have a password for root. I can't do any of those three. I have had this problem for a year.
I'm running Kubuntu. When I try to boot from the live USB to reinstall latest Kubuntu 22.04, I get this error, even though I haven't got a floppy disk on this PC.
I have the password of the only of user in the system if that helps, but it is not on the sudoers group. And I keep getting the message this incident will be reported. By now I don't know if I have ever set up a password for root or if I have forgotten it. I'm not dual booting in this machine. I can't access grub menu either since when I press Shift or Esc on booting, grub menu is not displayed.
Since I can't access sudo, I can't update the system.
This is the boot menu.
I don't know which of these option to choose to boot from the live USB.


