I use a browser extension which always redirect wikipedia articles to their mobile equivalent (chrome, firefox). I find this much less cluttered and much more legible but it hides the settings screen behind a burger menu, so I hadn't thought to look for a dark mode until I finally cracked late at night after being blinded one too many times.

It turns out that there has in fact been a dark mode available since July 2024.

So when on the mobile site, click the top left burger menu, click "settings" and then choose either "Dark" or "Automatic" modes and suddenly reading Wikipedia at night has become a whole lot more peaceful.