The install guide refers to the color scheme (light blue or not) of the initial GRUB boot menu for determining if the system provides UEFI or not. However, while it is true with the installed Funtoo systems, the Funtoo LiveCD provides a wallpaper for the boot menu so actually the method above does not work during installation.

We need to update relevant articles with an alternative method for UEFI detection. For instance, it works to see if ls /sys/firmware/efi/efivars succeeds.