As far as I know this is no longer true - there's an official firmware image that enables fastboot: https://developer.mozilla.org/en-US/docs/Mozilla/Firefox_O

As far as I know this is no longer true - there's an official firmware image that enables fastboot: https://developer.mozilla.org/en-US/docs/Mozilla/Firefox_OS/Developer_phone_guide/ZTE_OPEN#Device_revisions https://developer.mozilla.org/en-US/docs/Mozilla/Firefox_OS/... However I've not yet actually tried this on my ZTE Open.