Hacker News Reader

Darkreader is available for most browsers, desktop and mobile: https://darkreader.org/blog/mobile/

Also much more mobile friendly in general. I typically use HN more but tends to pull Lobsters up far more often on mobile. Even though I do have a user stylesheet for HN it still doesn't make it great on mobile and I can be bothered to fiddle with it too much myself.

Harmonic[0] has a dark mode.

[0]: https://github.com/SimonHalvdansson/Harmonic-HN

Dark Mode has been promised since 2020 but we still don't have it yet.

I use Firefox in built dark mode feature when browsing at night in mobile.