[waldo98]

Also, I've attempted to remove all USB devices from my Chromebox and I get the same error message, minus the top line.

that sounds like you updated from the Legacy Boot firmware to the EFI firmware - did you do that at the same time? Otherwise I'd just boot. LE 8.0 install media and choose the repair option

I updated the firmware from Legacy to EFI when I updated from OpenELEC to LibreELEC 7.0.2, which was a few months ago. Anyways, I realized that I was installing the Raspberry Pi2/3 version and not the generic AMD/Intel/NVIDIA version. Once I loaded the correct image file, I was able to re-install LibreELEC 8.0.