In fact, a light theme is not a default theme. We focus on the user's preferences specified in the OS (if the user uses a dark theme in the operating system, then the corresponding theme will be included on the site). Therefore, the logic of choosing a theme is violated here, if you specify a dark theme by default, since often it is a light theme that will be used.

Agreed - it looks like the D2 site has it somehow? Can't find how they have managed it from a cursory search through their code