Comment 21 for bug 1955109

@ Norbert (nrbrtx)
to overcome this bug, until some sort of fix is applied by the developers:

while logged into Jammy Jellyfish navigate to /etc/default/grub
and add the following line and save:

GRUB_DISABLE_OS_PROBER=false

After the edit, in the console, run:

sudo update-grub

The grub menu will be set up and other operating systems on the device will be displayed next time the system starts.

(Unfortunately this is viewed as a security problem, which has yet to be addressed.)