Chromebook and LinuxCNC

I would just try the stretch ISO image on the GXBT-1900, it should work as is.
You may need to unplug/disable the built-in wireless card if one is included

www.linuxcnc.org/testing-stretch-rtpreem...-uspace-amd64-r8.iso

That will be fine. Pretty sure its the exact model I'm using with my 7i76e
The Wifi card will cause massive latency so remove it and use a USB wifi dongle.

As Peter said, the iso would be what I would try first

I was considering if installing a recent version of Ubuntu on internal hard drive which, is a added accessory to GXBT-1900. Idea was if Linux CNC would boot up with dongle.

I think the ISO Peter linked to will make life so much easier for you.

Should Ubuntu or a Linux OS be installed on a hard drive to boot up Debian LinuxCNC dongle because of Shell?

I downloaded the ISO and copied it to a USB from a windows PC using Win32DiskImager. You need to rename the file extension to .img. Then I booted from USB.

I could never burn an ISO to a USB from Linux. I saw this was a known bug in some distributions.

I am thinking of getting one of these for the 7i76e board.

www.gigabyte.com/Mini-PcBarebone/GB-EKi3A-7100-rev-10#ov

You might be able to save some money by using a celeron based machine J1900 or N3160 which is all you need (by Mesa's recommendation. Aso the onboard wifi is pretty useless and most likely will cause unuseable latency so the big antennas will be useless as you'll probably need to use an USB wifi dongle.. If you look around, you should be able to find a similar machine with dual LAN ports and celeron cpu.

Experiencing some difficulty accessing LinuxCNC. It's been about a year since I booted to Debian 9 and opened LinuxCNC Axis a lot of times. Equipped with a Gigabyte GB-BXBT-1900, Ubuntu 16.04 LTS OS and USB Debian 9 Stretch LinuxCNC PREEMP. I think it's the very USB stick before booted to Debian 9. I think upon powering on the computer the BIOS was intercepted with F12 and a selectable boot drive which, is UEFI: USB Flash Memory1.00, enter and sent the GNU GRUB. I was only able to get to the GNU GRUB two out of many times recently and accidently went to Ubuntu instead of Debian 9. I think was suppose to select `C', press any key and boot to Debian. Would you know why not getting to the GNU GRUB screen often enough bye chance?

Optionally resetted the CMOS.

I did get into the GNU GRUB by repeatedly pushing the Shift key upon powering on.

Could of the 'Advance options for Ubuntu' and 'Ubuntu, with Linux 4.10.028-generic' been selected but 'UEFI: USB Flash Memory1.00' didn't send to GNU GRUB. Selecting 'Ubuntu, with Linux 4.10.028-generic' boots to Ubuntu 16.04 LTS OS. The Ubuntu desktop appears okay.

Still can't boot to Debian 9.