The 404 page doesn't load properly if the URL is deeper than the root, like https://docs.krita.org/en/user_manual/this-does-not-exist.html None of the styles, images and scripts are loaded. The search box and language switch also does not work as a result.
how weird... Looks like the paths get messed up :|
I think it's because the 404 page is built assuming it would be located at https://docs.krita.org/en/404.html and it uses relative paths to reference stuff, which wouldn't work when the page is loaded for deeper directories. One way to fix it would be to inject a <base> tag [1] into the generated 404.html to make it load relative to https://docs.krita.org/[LANG]/ . [1]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
So someone actually made a whole plugin for this, but it seems slightly overkill? https://github.com/readthedocs/sphinx-notfound-page