It would be a very pleasing user experience if we could enjoy the Server usage with a true dark mode. The customization in the Theme-Panel isn't advanced enough to do it ourselves - unless we deep dive into the css-files. The CSS already has a good structure and the dark mode could be enable with just a few changes.
Here is a comparison of my server in light and dark mode.
It's probably noticeable that I haven't studied Design, but it should give a rough suggestion how it could look.
Obviously not everyone wants a dark mode, therefore every user should have toggle in the user settings to switch between light and dark mode.