Collection of custom CSS files to override or compliment third party websites.
I use the Stylux add-on https://addons.mozilla.org/en-US/firefox/addon/styl-us/ https://chrome.google.com/webstore/detail/stylus/clngdbkpkpeebahjckkjfobafhncgmne?hl=en-GB
But, there are others available.
Use the Stylus interface to open a custom CSS editor, and then import the CSS directly. Example:
@import "https://raw.githubusercontent.com/chrisgdouglas/custom_css/master/searx/nord_searx.css";