It sounds like the boot rom not loading is an actual hardware failure. I say this because some of the basic steps you have taken, and then verified via command line flash using a real Ubuntu host, would tend to rule out most of the errors which might be made in the flash process itself.
You could try from a different PC host just to see if you get the same error when the PC changes. Some rare PCs have USB problems (even when not a VM), but the boot rom not running tends to not be a USB issue.
Deleting your PC’s downloaded software, and then downloading and trying again with new software might validate if the actual software you were using to flash with is somehow corrupt.