Trying to get away from my phone more, and an e reader sounds like a good way to get myself to read more. Kobo is sounding like the most recommended one based on some googling, but I’m also ok with jailbreaking something like an older kindle from eBay. Something that plays nice with Libby would be ideal but not required. 
I’ve used KOreader exclusively for a while and had no idea it was a Kobo thing. I actually have stayed away from e-ink stuff because I wasn’t sure how my dubiously acquired collections of books in various formats would work on it. This is convincing me to get a Kobo lmao
Even on a stock Kindle you can load pirated stuff very easily
I guess I just assumed that all these e-readers were pretty locked down since they are made and sold by publishers. And my FIL has a kindle and spends a ton on books. But I think I want one of these color Kobos now, when I can get up the cash
You can just connect a Kindle to a computer and drop anything on it. Most books are in epub format but Calibre converts to azw3 with no issue.