Highlighting the very popular app enabled by this, KOReader: https://koreader.rocks/
It's way better than the built-in Amazon reader app.
There's however a dark mode still if you need it; go to the gear icon, screen, auto warmth and night mode. Tap the mode line to switch it from automatic settings (either on time schedule or coordinates) to manual.
[0]: Basically, E-ink displays have to fully "reset" their screen by repeatedly toggling the pixels on and off, since they can't fully toggle themselves off normally; doing so will leave them with a bit of grey. Because this isn't very friendly on the eyes, most displays usually do this every couple "page changes" (actual pages when reading or moving in a menu.)
When you're using a device actually for reading, you don't care about minor defects on the page, just like you wouldn't care about some stain on the page of a paper book when reading it.
I hate the idea of my book collection being chained to Amazon by DRM, absolutely hate it. This whole DRM mess is one reason I haven't bought a dedicated e-reader.
Though, to be frank, it's not the only one, I spent a jaw dropping amount of money on a really good hardcover copy of The Lord of the Rings recently, and I feel like no ebook will ever come close to the reading experience of that thing. There is something about this immense, weighty, hardcover tome that just commands your attention and I still find that print on good paper causes less eye strain than even the e-ink screens I've used (though they are pretty good).
Edit: it has AskGPT!