Simple Dark Theme style for any website which you can configure per-site
< Обсуждения Universal Dark Theme Maker
You can try installing it with other manager, but if it won't work - that means that manager is missing some important features without such this script won't function good enough
greasemonkey has abandoned its massive userbase long ago with random core changes with no backward-compatibility and horrendous user interface which only got worse over time, so userbase abandoned it in return. It might be a bit faster than others now but only because it's missing needed features.
Is there any way you could consider configuring this to work with a different manager, like violentmonkey or greasemonkey? Seems amazing.