We have a standard 4K stick and yesterday I looked into replacing the launcher. Unfortunately it seems that Amazon have stopped users from accessing ADB or an ADB shell making it almost impossible to customise it. It may still be root-able but I wasn’t that desperate to change it.
I’ve settled on Thunder. The only downside is that they haven’t implemented replying to direct messages yet, you can only view them but apart from that, it’s good.
That’s the problem. I think Amazon have been locking the device down. Rooting maybe the only way if that’s still possible.