Ubuntu disappeared from Grub menu

[cyberfriend-d]

I installed Ubuntu to work as a second system in early May. I updated my Ubuntu version from 20 to 22.
Today, the OS just disappeared from the Grab menu.
I press F11, I see a choice between Win11 and Ubuntu, I choose Ubuntu, but then only Win11 and UEFI settings remain from the options. I connected the drive to WSL2, checked the bootloader, nothing out of the ordinary, but Grub doesn't see Ubuntu...

[hakuna-m]

Probably, the upgrade uninstalls package lupin-support. Package lupin-support contains a script which creates a GRUB menu for a Wubi installed Ubuntu.

If the menu does not exist, you can manually boot with the following commands from GRUB menu (enter it on command line or edit a menu entry)

search -s -f -n /ubuntu/disks/root.disk
probe --set=diskuuid -u $root
set root='(loop1)'
linux  /boot/vmlinuz root=UUID=$diskuuid loop=/ubuntu/disks/root.disk ro
initrd /boot/initrd.img

If that works und you can boot into Ubuntu, install Grub script 10_lupin from terminal.

wget https://raw.githubusercontent.com/hakuna-m/wubiuefi/master/data/custom-installation/patch/10_lupin -O 10_lupin
sudo cp 10_lupin  /etc/grub.d/10_lupin
sudo update-grub