I would like to contribute on this.

Hey, sorry for the late reply.
The code for the frontend of the librespeed.org is hosted here: https://codeberg.org/librespeed/librespeed-frontend

Keep in mind that the UI in this repository is meant to be used as an example/template so adding a dark mode here would just make the examples unnecessarily complicated to read.

@adolfintel but we would add new css for styles and few lines of js for making the switch button.

If you're so keen on adding dark mode into the main repo (which I've been opposed to for years btw 😆) I suggest you use the @media (prefers-dark-interface) media query in the CSS instead of adding a button, that way it will follow the user's system preference.

I still think you should do it only on the librespeed.org website though, the examples are already long enoguh.

Ok 😅
Thanks @adolfintel

Have there been any updates on this 😅
I just deployed this as a Docker container and honestly it works great, the only real downside so far is that it basically flashbangs me whenever I open the page 😆