You can edit Grub so that it always appears.
Then, it’s easy to select an alternative kernel or even UEFI settings.
sudo nano /etc/default/grub
Here’s an example:-
GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=10 # or however many seconds for your own comfort
GRUB_DISTRIBUTOR=`( . /etc/os-release; echo ${NAME:-Ubuntu} ) 2>/dev/null || echo Ubuntu`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""
Don’t forget to run:-
sudo update-grub