As CSS and JS it should be possible to use this either as a gadget only (no install) or as a user script and css, but how? Tye js needs modifying to do this.
Topic on Extension talk:DarkMode
You can set it up like it's done on English Wikipedia. See w:Wikipedia:Dark mode (gadget) for instructions.
There seems to be quite a bit of divergence between the gadget and the extension. Maybe something can be done to sync them?
- The gadget CSS has received a bunch of edits, some requested after MusikAnimal's last edit: https://en.wikipedia.org/w/index.php?title=MediaWiki%3AGadget-dark-mode.css&diff=1172905668&oldid=1101625928
- The extension CSS has got 6 new commits in 2023
- The gadget JS is, well, a lot less functional than the extension thing which has an icon, but I suppose whether to change it would require a discussion