anything you can either freely install whatever software or epubs you want on it without paying Bezos or a kindle or nook you can jailbreak i suppose
Kindle has the market in a chokehold. USB C, warm light, email library sync, support + warranty, etc
the-ebook-reader.com/kindle-comparison.html
The Scribe is kind of a new market for "e-ink tablets" which I think is a dumb gimmick. You could always just ignore the gimmick features tho.
The most decked out reader models are prob these:
Kindle Paperwhite Signature Edition (no physical buttons)
Kindle Oasis 3 (not USB C)
I also just wouldn't buy anything new. The secondhand market for e-readers is great.
Amazon Warehouse (Kobo models here as well)
UnclaimedBaggage (Better deals on Kindles, less quality control)