I know that it allows you to put any books you like on it if you jailbreak it, but I'm not really sure where else I can buy ebooks and the money goes to the author.
Also I actually quite like the default reading experience (I have a paperwhite) and jailbroken stuff often has less polish.
You can install a much better reader (such as KOReader), any software you want (games and the like), and remove all calls to amazon servers - the later being especially useful if you buy the cheaper, ad-supported Kindle; allowing you to remove all ads.
You can call Amazon or contact customer support and just act like a dumb boomer who doesn't get tech and they'll remove the ads for you, just ignore them when they explain why they're there and keep saying stuff like "I don't understand what this is for I don't want this on my screen please remove it grandson"
The device will still call home though; which sucks in terms of privacy and also allows amazon to potentially delete your books remotely.
yeah i just never connect my kindle to the internet lol.
I have a quite old kindle, I don't think it has these things