Restoring the UEFI boot menu item for 24.04 encrypted internal volume using the install media

A Dell firmware update caused the Dell UEFI boot menu to lose the “ubuntu” item, and selecting the boot menu item for the NVMe device instead does not boot successfully. The NVMe device has just Ubuntu 24.04 on it in the normal LUKS-encrypted LVM setup made by the graphical installer (originally installed 22.04 and then upgraded that).

Previously when a Dell firmware update removed the “ubuntu” boot menu item, I was able to resolve the problem by booting from the install USB stick to its grub menu, choosing “Boot from next volume” (which booted from the internal NVMe), and then updating grub when booted from the internal NVMe device with the root volume on LVM on LUKS.

Now telling grub to boot from the next volume goes into Dell’s firmware, which either states that no bootable devices were found or offers to download Dell’s recovery tool (I didn’t proceed).

I am able to boot into the live USB system if I choose the safe graphics option in the grub menu for Ubuntu 24.04.1 USB install medium. (From there, I can see that the NVMe device is readable.)

When booted into the live USB system in the safe graphics mode, how can I tell update-grub or another command to set up a UEFI “ubuntu” item for the encrypted-root-volume already-installed system on the internal NVMe drive?