Fediverse

It uses the browser preference for light/dark theme by default

This doesn't work for me. It seems like you are using leptos_use::use_preferred_dark with server-side rendering which unfortunately uses the experimental Sec-CH-Prefers-Color-Scheme header which isn't supported by all browsers, e.g. Firefox.

In my opinion, it is way better to implement theme switching on the client side. The prefers-color-scheme media query is better supported across browsers and allows reacting to a change of the user's system preferences.