HD 8 cannot be downgraded. Will result in perma brick.
Just learned it the hard way. Tried to downgrade my Fire HD 8 (7th gen) v126.96.36.199 to the version 188.8.131.52 using the file "update-kindle-184.108.40.206_user_579225620.bin" and, as you said, hard bri...
Another success story here!
Just downgraded my in Dec. 2017 purchased Fire 7 (7th gen) from 220.127.116.11 directly to 18.104.22.168, using the image update-kindle-22.214.171.124_user_579225620.bin.
Everything went very smoothly. After the update, the first things...