How would you do this though, sideloading isn't that advanced is it? Or do you mean with a bunch of tools you can somehow somehow go somewhere in close to system files.
too bad they don't offer self-repare for things like the apple watch, I pad, Airpods, or something like that. Next to the IPhone, the Appple Watch is next to break because of it's constant exposure to everything.
Jailbreaking is not illegal. It used to be, however, Apple eventually decided to let it slide. The history as to why and what it took to get to such a conclusion is a whole can of worms to sift through so I won't go into major details about it. But essentially, it comes with one exception. If you do end up jailbreaking, you're essentially just voiding your warranty. Meaning that if you damage it, or something happens, you're on your own. If you wish to get support from Apple with a jailbroken device, you'll be talking to a wall, since jailbreaking is like I said, frowned upon and discouraged by them, and has a consequence, but is not illegal.
Are there still jailbreaks available for somewhat new iOS versions though? I have heard barely anything about them the last, what, 3 years? Edit, there do exist a lot of fake scam ones, still. Surprising enough.