I have managed to install the new kernel however after a few reboots the system is still using the old one, and there is no option to remove the old one either (doing so I thought might “trigger” the system to use the new one, but that is moot as I cannot uninstall the old one anyway). How does one…

it looks like /etc/default/grub has got mixed up some output messages from the terminal. Could you have pressed the middle mouse button and pasted output from the terminal in there? Do you have a backup for that file before editing? here is mine: GRUB_DEFAULT=saved GRUB_TIMEOUT_STYLE=menu GRUB_T…