I think this is past due - every time I open the blog or the main site, my eyes will hurt for a little bit because everything else is in dark mode, but both of the sites are completely in light mode with no toggle. Imagine being in a dark room and turning on a flashlight pointed directly at your eyes.
Especially when it’s dark, it’s really hard to look at blog.discourse.org or discourse.org without instantly leaving due to the lack of a dark mode. It’s less of an issue during the day, but especially at night, it needs a dark mode switcher.