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) v184.108.40.206 to the version 220.127.116.11 using the file "update-kindle-18.104.22.168_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 22.214.171.124 directly to 126.96.36.199, using the image update-kindle-188.8.131.52_user_579225620.bin.
Everything went very smoothly. After the update, the first things...