I prefer to use darker interfaces on most websites I use so I change the looks of many websites with Stylus.
On Safari I use Safari Stylish.
Below are themes I love using with it.
Use it together with RES night mode
I also use WikiWand as my wiki dark mode:
In the cases where there doesn’t exist a Stylish theme for a website, I sometimes use Nightlight Safari extension to have all websites have night mode with a toggle on/off switch. It works surprisingly well and helps when using the internet at night.