[Matt Devo]

If you don't care about regaining the disk space allocated to ChromeOS, then simply flashing the coreboot firmware is sufficient

Thanks Matt. I appreciate the help. I don't really need the space taken by Chromeos, just trying to avoid 30 sec delay.

By the way, is there some way to back up the kodibuntu system on Chrombox to usb drive?

if you just want to get rid of the boot delay, then you can use the script to set it to a 1s delay and default to booting Kodibuntu. But if you have no plans to use ChromeOS then flashing the standalone firmware is a better option.

I'm not aware of any specific tools for backing up a Ubuntu system, though I'm sure some exist. If you only care about the Kodi settings etc, then there are add-ons available to back that up.