You can download and install third-party apps from the Amazon Appstore, and while Amazon doesn’t publicize this fact, it’s also possible to sideload third-party apps. That gives you permission to change system files that would otherwise not be accessible to a user account. It’s also worth noting that this method for gaining system user access is temporary – it doesn’t survive a reboot. But any changes you make while you have system user status will remain. But the longer you wait, the more time Amazon has to roll out software updates that will stop them from working in the first place.