That's the thing with SSR... (i.e. with Next) or with pre-rendering apps before hand. In the initial GET request to the page, you also send a cookie with user

That's the thing with SSR... (i.e. with Next) or with pre-rendering apps before hand. In the initial GET request to the page, you also send a cookie with user preference. Depending on their dark mode preference you can style the page to be in dark mode as part of the server or pre-rendered markup -- no JS required :o. Now.. how difficult that is to do with Gatsby I don't know. But the fact that someone shot themselves in the foot with Gatsby, then learned to hobble along on one foot isn't a cause for celebration imo.