Earlier quoted context omitted.
My old kindle is a Kindle 3 from 2010, and it's still my primary e-ink reader. I still haven't found a compelling reason to upgrade.
I gave up on my first paperwhite last year (10+ years old). Would randomly lose its charge, which was annoying when bringing it on trips (and often not having an old micro-usb charger lying around). And from being stuck into all kinds of pockets and bags without a protector (half the use was it fitting in my pants) had seriously scratched up the screen. The new one I got is nice, but other than the old one being beat…
I jailbroke it and installed KOReader. Suddenly, no delays, great interface, wi-fi sync with Calibre. I might replace the battery one day, but it still lasts 2-3 books.