Instead doing this on a site-by-site basis, consider using an extension like DarkReader (for mobile, some chromium Android browsers and also Firefox Preview allow extensions). It degrades performance a bit, a small fraction of sites look broken by it (can selectively disable), but its a huge boon overall.

UserScript: https://gist.github.com/1player/85d146a4aa0c2afc78bab63582f5...

Cascadea CSS Script: https://gist.github.com/1player/af5f02ccbe7c930f793fc104c999...

Not perfect, tested on Safari, gets the job done. Changes automatically based on your system preferences (light during the day, dark after sunset)

On Chrome 78+ (including mobile, at least Android)

    chrome://flags/#enable-force-dark

works pretty well. Made a big difference to my evening browsing.

On Chrome, I use the Dark Reader extension. Works perfectly well with HN, and I use it with many, many other websites.

> Somewhat off topic, but has someone created a dark mode stylesheet or viewer for Hacker News?

I use Materialistic on mobile, and it has a dark theme. On web, I just use a dark theme extension for sites in general.

On Brave browser for Android, I use chrome://flags and enable "Android Web Contents Dark Mode".

Samsung's Internet browser has a Dark Mode toggle built in, which surprised me.

There's the HN Special add-on for Firefox and Chrome. It lets you set a dark style or also use an alternate stylesheet for HN.

Install stylus on your browser and look for a hacker news dark mode.