I agree with the Kobo recommendation. They’re great devices. However, OP specifically mentioned azw3, which is Amazon’s format, right? You’re not going to be reading eBooks from Amazon on a Kobo. Your choices are DRM-free ebooks, or books from Kobo’s serviceable, but kind of crappy, store. Also, in most cases, pdfs are going to be practically unreadable on any Kobo; you need something more in the format of a reMarkable to get usable pdf on an e-ink device. PDF was another requirement.