The bootloader needs to be on an MMC device. It does not read from USB. You can flash the bootloader on a small MicroSD card using libretech-flash-tool and leave it inserted to boot the OS from USB.
The bootloader needs to be on an MMC device. It does not read from USB. You can flash the bootloader on a small MicroSD card using libretech-flash-tool and leave it inserted to boot the OS from USB.