For desktop, I use the refined hacker news extension (github: [0], show HN for i...

For desktop, I use the refined hacker news extension (github: [0], show HN for it: [1]) which allows you to set custom CSS. It has a dark mode setting but I prefer the following CSS which makes the entire background black and the text white (Screenshot: https://imgur.com/a/2lcy1Ga):

  :root,
  html { 
     background-color: white;
     filter: invert(100%);
  }
  
  * { 
     background-color: inherit;
  }

Another great thing about the extension is when you go back to the same thread, it gives a little highlight to new comments that you haven't seen before so you can quickly find them. Only downside is that that doesn't work for comments after the first page.

[0]: https://github.com/plibither8/refined-hacker-news

[1]: https://news.ycombinator.com/item?id=20173974