I’m running the app successfully on my tablet. Try this: https://forum.xda-developers.com/amazon-fire/general/amazon-fire-utility-tool-bloat-removal-t3641151
I also had a post about it: Replaced My Existing Security Panel with Konnected Security - My Writeup and you may be able to just follow what I did. Can’t tell you the exact step other then mine works just fine.
Your tablet probably came out of the box as v5.4.0.0 which the bloat removal should work decently for. If it updates to 5.4.0.1 then it won’t work. If you factory reset it you can go back to 5.4.0.0 then at the WiFi setup screen click hidden network then back and you can skip connecting. Then you can run the debloat stuff and prevent it from updating.
This of course is only if you’re ok getting rid of the Amazon stuff and replacing it with Google stuff. I was because I’m using mine only for SmartThings/ActionTiles. You might not be.