I’ve been able to create a SD card image using ubuntu-cn9130-cf-pro-mmc_1_2.img and have it boot. I tried the same thing ( using ubuntu-cn9130-cf-pro-mmc_1_2.img ) with a USB Thumb Drive following the instructions but it doesn’t seem to work. Then I’ve made an image of the SD card and then have used this to create an image on a USB thumb drive. This image does not boot up. I’ve even changed the setenv boot_targets ‘usb0 mmc1 mmc0 susi0 pxe dhcp’ in uboot but this doesn’t seem to help either. I have tried the switch settings for SPI and MMC and it does seem to help.
The board can not boot directly from the USB drive, you need to have u-boot flashed to boot device and then from there it should boot from the USB drive. If this is still not working please record the console logs and post them here so we can review them.