If you need to downgrade the Kernel version on Ubuntu Linux, here's how you can safely do this with the linux-image and related packages.

ck@ubuntu:~$ dpkg -l|grep linux-image
ii linux-image-5.15.0-73-generic 5.15.0-73.80 amd64 Signed kernel image generic
ii linux-image-5.15.0-75-generic 5.15.0-75.82 amd64 Signed kernel image generic

ck@ubuntu:~$ grep TIMEOUT /etc/default/grub
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=0

Change the values to:

GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=5

Followed by the command sudo update-grub. At the next system (re-)boot, the GRUB menu should show up.