Could not get a Geobook3x to boot with a USB drive UEFI Linux / Windows. After numerous tries using Rufus and Lubuntu, Ubuntu and rescue disk images - the Geobook refused to boot via USB.
Solution is to use Umi Multiboot USB creator to create an Ubuntu (or whatever) USB drive.
You can also use the Microsoft Media Creation tool which creates a Windows 10 bootable USB drive.
BIOS settings on the Geobook should be: You have to hit Esc on boot to get to the Bios. Select Chipset -> South -> Linux. Then choose Boot and set the USB stick as the first bootable option, followed by the standard UEFI boot loader. Save the settings, BUT the Geobook also lets you boot straight to the USB in the Save screen. Do this and hopefully it should boot to Ubuntu!