Feel that the partition table looks good there, might just be a bios setting to get this booting again.

You could always mount these partitions and take a peek at the files, cd and ls with nano / vi on relevant files that are human readable.

Secureboot is my gut feeling, possibly paired with a side of CSM as to what’s prohibiting your system from booting. Could be the /boot partition is cooked too but looks like it’s at least there and listed.

From remoting into one of my systems reading a file via nano in /boot/loader/entries

Believe the same thing as you are experiencing has happened to me on my x99-WS-IPMI board due to its age. Hopefully the CMOS battery is easy enough for you to replace on your board, if that’s the failure.

Great point on the cmos battery. Always a fun game remembering what the bios setting were to have booting again. CSM can also be an arsehole here.

In a live enviornment does the disk show any partitions? Maybe your boot partition is somehow corrupted.

From the terminal in the live enviornment run lsblk

Output should look something like this (sorry formatting)

user@pc ~ lsblk

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS

sda 8:0 0 931.5G 0 disk /home

sdb 8:16 0 931.5G 0 disk

├─sdb1 8:17 0 1G 0 part /boot

├─sdb2 8:18 0 32G 0 part

├─sdb3 8:19 0 64G 0 part

Yeah that’s probably a sad truth for those in the good ol’ USA.