Since such a screen would be most usable outdoors, I wonder about the setup. I guess if it'd be light and thin enough it could be put on top of the screen in that case? Or would you have a separate stand for it?

I would think a seperate stand. So I can put it behind the laptop and get it to eye height.

E-ink monitors already exist. Look up the Dasung e-ink monitor.

That might be an option. Have you tried them?

I have one and use it outside regularly (e.g. [0]), it's pretty amazing!

There's some open-source tooling[1] for it which can control screen features like brightness/refreshes/rendering modes/... and I've set it up[2] to work with my unprivileged user so that I can bind these features to keys in my Emacs.

With these screens you want to use light themes, and use tooling to improve contrast on websites (a friend wrote a Firefox extension[3] which is amazing for this).

[0]: https://photos.app.goo.gl/eGgGYR7ecBqv9gqy8

[1]: https://github.com/leoluk/paperlike-go

[2]: https://cl.tvl.fyi/c/depot/+/3029

[3]: https://github.com/adisbladis/einkmode-firefox