I have a working installation of Antergos, and do not want to reinstall. My main SATA port on my laptop is failing, and I need to move my SSD to an enclosure in the DVD drive slot. The problem is that my bios doesn’t allow booting to an SSD in that tray.

As a solution, I’m trying to install GRUB to an SD Card, so I can boot to the SD Card and have that boot from my SSD. I’ve followed the instructions on the archwiki.
Installation drive = sda
Live USB = sdb
SD Card (Bootloader destination) = sdc

First I have to arch-chroot into my Antergos installation, since I can’t boot into it.

sudo mount /dev/sda2 /mnt
sudo arch-chroot /mnt

Then I follow the instructions on the archwiki

mount /dev/sdc1 /mnt/usb
grub-install --target=i386-pc --debug --boot-directory=/mnt/usb/boot /dev/sdc
grub-mkconfig -o /mnt/usb/boot/grub/grub.cfg

grub-install finishes with no errors reported.

grub-mkconfig gives a few errors.

ERROR: mkdir /var/lock/dmraid
ERROR: mkdir /var/lock/dmraid
ERROR: mkdir /var/lock/dmraid
ERROR: mkdir /var/lock/dmraid
ERROR: mkdir /var/lock/dmraid
ERROR: mkdir /var/lock/dmraid
ERROR: mkdir /var/lock/dmraid
  WARNING: Failed to connect to lvmetad. Falling back to device scanning.
grub-prove: error: cannot find a GRUB drive for /dev/sdb1. Check your device map.

I’m not too worried about the grub-probe error because /dev/sdb1 is my live USB, so I don’t think GRUB should find that anyway. I’m not sure what the mkdir /var/lock/dmraid error is. Or the Failed to connect to lvmetad error. (The system was never setup with LVM).

Any suggestions would be greatly appreciated. I’d prefer not to have to reinstall, because I have my system setup just the way I like it.

The final result of this is that I can boot from the SD Card, but it brings me to a Bash-like GRUB Shell. I cannot figure out how to boot to my Antergos installation from there.

EDIT: I decided to take the plunge and reinstall, choosing the SD Card as the bootloader within cnchi.
If you know the solution to this issue, feel free to provide an answer anyway, as it might help another user with the problem.

EDIT 2: Even on the fresh install, I got the same issue. I chose the SD Card as the boot device in Cnchi. After installation, my system booted to the Minimal Bash-like Grub Terminal. Any help appreciated.