There are 4 repositories under userstyles-themes topic.
A user style to customizably darken the Google Search website
Dark userCSS styles to use with Stylus addon.
Repository for the Roblox Legacy Old Theme.
Perhaps the best dark theme for VK
Repository for my custom userstyles
best redesign theme for youtube
New dark mode for spigotmc.org
Fosstodon/Mastodon CSS Stylesheet
Collection of personal User CSS for Stylus.
A generator for UserStyles
A dracula colorcheme inspired dark theme for the fast.com internet speedometer website
Dark userstyle for miraheze.org
Personal Cascase Style Sheets Library for use in Stylus and Firefox.
A Stylus dark theme for Flipboard
A solarized dark theme user-style for Quora using Stylish
A zenburn dark theme user-style for Quora using Stylish
Stylus theme for https://mokum.place
My custom theme for lucida.to with real dark theme.
Meduza Gorgona - a dark colored theme for Meduza.io
Userstyle for Bexio to make it look much cleaner and dark