Trying to understand Grub in 26.04 with unsuccessful booting

[peterwhite23]

@paddylandau

I should state, because I realise that I didn’t make it clear, that I had successfully booted into the system. This problem arose only after I changed /etc/default/grub, ran sudo update-grub, and rebooted.

I suspect that resulted in an effectively empty menu, except for the UEFI option. Can you rewind to a snapshot prior to this change? Then do exactly the same, show the output of update-grub and the menu section of /boot/grub/grub.cfg. On a side note, it’s probably best to leave /etc/default/grub alone an put drop-ins in /etc/default/grub.d/.

As for the two GRUB menus, I think that’s due to the two-stage boot with secure boot. At least that’s what I gathered from this:

@mkukri

You see with an encrypted /boot, as an attacker with disk access I can just as easily modify your ESP where your GRUB lives and modify GRUB’s initial bootstrap configuration (on the ESP) …

(emphasis added)
That bootstrap grub.cfg is in /boot/efi/EFI/ubuntu/ on my 24.04 installation.