I was being lazy, I should have opened a newish Mint and figured out the easy way of updating the Mint kernel.
a) Open the Update Manager
b) Open the View tab (what a stupid tab to use!). Select Linux Kernels. If you have never done this before it will trigger all sorts of dire warnings of Doom such as your nadgers dropping off. Ignore this carp. and press OK (I think)
c) A simple tab will open. Select 5.15 to get the latest stable Kernel with the missing security updates, and install it.
d) I guess you could use the previous screen to remove old kernels, but I prefer to open a terminal and type
sudo apt autoremove, then OK and this will remove all the old kernels and associated cruff.
then just make sure you are ok by using
sudo apt autoclean, and sudo apt apdate, then reboot
After a while the Update Manager will update your kernel to a slightly more current version
.
