GitHub finally has a dark mode. You can enable it in the settings. There are three options: system (automatic light or dark based on the system preferences), light and dark. Now I can better scroll through code at night or early in the morning. ☺️ Gitea (my preferred code hosting system) has a dark-mode too, but it’s more like a grey-green mode.
I generally prefer dark user interfaces wherever possible. My phone is set to a dark mode (as far as there is a dark mode in Android Pie), apps like Telegram are set to dark mode and on the desktop I prefer dark modes too. But the most important software I use everyday is a web browser. And most websites don’t support a dark mode yet (because there was no native browser feature for that until recently).