I have an HP machine with only Ubuntu installed. I want to boot into to a different kernel version.

Holding Shift during boot is not effective. Holding ESC however opens up another menu, not the usual GRUB menu with Ubuntu, Advanced Options for Ubuntu, Recovery Mode, etc.

It has options like:

F1 - System Information F9 - Boot Device Options

F10 - BIOS Setup

F11 - System Recovery

Enter - Default Startup

How do I enter the GNU GRUB Menu?

I also want to avoid modifying the grub file for now.