As usual, this WILL
void your warranty and I am NOT
responsible for anything you do with this. Installing it properly won't brick your Fire TV, but doing stupid things with it might.
First, you must be unlocked. You can follow the instructions here
for making that happen.
If you are first starting, you should first unlock, then install this ROM, and THEN install Magisk for root or any other addons. This rom uses addon.d to preserve Magisk and any other addons, but any system modifications like Magisk, gapps, etc, that you have installed prior to this ROM will NOT be preserved.
If you've already unlocked and installed Magisk, then after installing this ROM you need to reinstall Magisk in TWRP.
Starting with 184.108.40.206, Magisk is always installed.
Beyond that, Magisk and any other addons will be preserved as you flash newer roms.
Consequently, if you would like to remove root, you will need to wipe /system in TWRP prior to installing this ROM. That will prevent it from being restored when installing the ROM.
Thanks to @k4y0z
for the unlock.
NEVER FLASH A STOCK ROM >= 220.127.116.11 AFTER FLASHING 18.104.22.168_r2 OR LATER! THIS WILL BLOW AN EFUSE.
Changelog and Downloads: