GitHub introduced dark mode:

From sites I use, dark mode is supported on Twitter, Slack, GitLab,, Gmail, ProtonMail. Some others, like Jira, doesn’t have themes yet, so Dark Reader is a solution but it makes the page load is a bit slower.

Yeah, a few months ago I had a post how researchers say that light mode is better for eyes but I can’t get used to it, my eyes definitely get tired of a white screen. Bad background lighting? Glasses? I’m not sure what’s the reason, I need a bit more experiments.