[Matt Devo]

Thanks for quick reply Matt. Question is to boot from live USB, do I need to intervene with any keys or it just boots directly after power up?

 assuming you did a standalone setup a few years ago, you likely need to press ESC for the boot menu when prompted, then select the USB from the list. What I would recommend though is probably to boot a Linux USB, update to the latest UEFI firmware using my script, and then reboot / do a clean install of LE. You can always back up your userdata before / restore it after using the built-in LE backup/restore function.