I use some hacked together uBlock Origin filters that do a fairly decent job at giving HN dark mode if you care to take it for a spin:

    ycombinator.com##html:style(background-color: #3e3e42 !important)
    ycombinator.com###hnmain:style(background-color: #2E2E31 !important)
    ycombinator.com##.age:style(color: #ccc !important)
    ycombinator.com##.c00:style(color: #ccc !important)
    ycombinator.com##.comhead > a:style(color: #dedede !important)
    ycombinator.com##.comhead:style(color: #dedede !important)
    ycombinator.com##.hnuser:style(color: #ccc !important)
    ycombinator.com##.subtext > a:link:style(color: #ccc !important)
    ycombinator.com##.subtext > a:style(color: #ccc !important)
    ycombinator.com##.subtext:style(color: #ccc !important)
    ycombinator.com##.title > a:style(color: #dedede !important)
    ycombinator.com##a:link:style(color: #ccc !important)