For those who want to root Kidle by using Kingroot, here are the steps that you should follow. The first one is to make sure that you have 18.104.22.168 fire OS installed on device. to do this step, you can go to Settings > Device Options > Software Updates to check the version. If your device shipped with 22.214.171.124, then you do not need to load the different firmware. As for the mileage, it may vary. Do not forget to not try to downgrade a>126.96.36.199 device below 188.8.131.52 as this will brick your fire.
The second one is to rest to factory settings. You can do it by going to Settings > Factory Reset and performing the factory reset. Apparently, this step will reboot your device. when the device boots, please skip all set up and do not connect to WiFi yet as it will slow down any unwanted update process.
The third one is to enable Developer Mode. To do this, you can go to Settings > Device Options and tap the build number seven times to make the developer mode enabled. Then, go to Settings > Device Options > Developer and turn on USB Debugging and ADB.
The fourth one is to download the needed files. You can download the newest version of SuperTool from Root Junky and extract it somewhere you will remember. You also have to download the latest Nexus ROM for Fire Tablet. However, you do not have to extract for this one.
The fifth one is to run he SuperTool. When you are in Command Line, please navigate to the SuperTool folder and run the appropriate file. The Linux command is $ ./3-Amazon-Fire-5th-gen-linux-mac.sh. then, press 2 and enter to root your device. first of all, it will install Kingroot to your device that you need to run from the device when directed to do so. Apparently, Kingroot will ask you to connect to WiFi. It is stated that you will likely have to run Kingroot several times before it will work. As it might take some times, feel free to spend your spare time by watching a movie or listening to music. Every time you run Kingroot, it will reboot the device a few times and show you the progress on the screen. For your information, it will take about 10-15 minutes or more per attempt. Once it is working, you have to plug your Fire back into the computer and continue the SuperTool process. This one will install SuperSu that will have interaction from you on the device. all you have to do is to follow the setup procedure according to the instructions in SuperTool. When the process is done, please run “Block OTA updates” in oredr to prevent the accidentally losing root access.
The sixth one is to install Rom FlashFire and the last one is to enjoy it. with the new Rom installed, please make sure to update Google first. After it is updated, clear Google App and framework cache and reboot your device.