Hm.
"3. Now start your notebook and immediately press ESC, F7, F10 or F11 (varies depending on the device) repeatedly until the boot menu opens where you now select your USB stick with the arrow keys and confirm with the Enter key."
After trying the Fn keys first (of course) I try ESC and land in... not the boot menu.
Instead I'm met with a "grub> " prompt.
None of the available commands seem to know or care about booting from a USB device.