It’s unfortunate that Kindle doesn’t support EPUB but it’s easy enough to convert with Calibre, and some free book providers (like Standard Ebooks) provide compatible .azw3 for download.
Even though I’m not keen on how locked down Kindles are and their software and rendering quality could be improved, the physical form factor and ability to sideload is enough benefit that my next ebook reader will be a Kindle too, unless something clearly better comes along.
Peak Kindle.
A friend who got a recent Kindle was not able to use it at all without linking it to his Amazon account. He could sideload books only after that. I'm also not sure how firmware updates work without connectivity.
I have little interest in installing custom software for an appliance, so it would need a very good hook if the default reader is so bad most people are replacing it.
> that isn't a 7" screen running basic Android in a crappy case
Boox devices run Android, but in relatively recent versions and the system isn't that bad. And you can install any Android App (even the Play Store, but why bother when there are F-Droid and Aurora).
The Sony Digital Paper series isn't (wasn't?), I don't think Onyx Boox ones (which are definitely not discontinued) are, either.
I’m afraid that I won’t be able to establish the habits necessary to make the purchase worthwhile, however.