Unfortunately not possible on the Fire Stick (4K Max), Amazon have modified it to disallow other launchers; there are some "hacks" but none have worked for me and the closest one I did get to working was too much of a pain for the rest of the family.

I've found no way to root it either so I just want rid of it, every time something appears almost-full-screen on the home page that's inappropriate for the kids with no regard for what time of day it is, my wife gets all the more annoyed by it; she never wanted it in the first place, so the poor experience is not helping my case).