While I don't disagree, I still think using a Kindle device is stupid.
No reason that they can't just go 'oh we didn't sell those books, we should clean up all that unauthorized content' at some point in the future.
Buy something that's not made by Amazon, even if it costs a bit more or has worse features, because well, they're not to be trusted.
(Or custom non-connected firmware if that's a thing for Kindles. Never really looked so no idea if that's a thing.)