Nothing. What people think and say is jail breaking is actually side loading custom android apps, which is actually already part of android. Amazon IMO made it more difficult than it’s supposed to be. I installed vlc and stremio and use it alongside all the other apps. Nothing groundbreaking nor illegal. That’s not jailbreaking, it’s using Android the way it’s designed to be used.

I’ve never tried it, but there appear to be some rsync apps on f-droid, you could try.

Wow, what a short-sighted view. Android, despite its many shortcomings, gives you orders of magnitude more freedom in almost every way imaginable. And none of its shortcomings are blocking you from using it, rather more or less annoy you.