Can you explaine how did you make a bootable of Linux Mint?
Also what do you see when you try to boot from the USB? And Linux Mint should be able to boot from UEFI without any issue.
Can you boot into linux mint using the same usb stick into any other computer? Reason some usb are not supported to be a bootable device.
I suspect that GN31 have 32bit efi boot so maybe it only reads boot32.efi file. I am not 100% sure about it as I don't have the device to test, but I will try to help you as much as I can.