This is the one true uBlock Origin by Raymond Hill. It is not to be confused with that other uBlock which allows "acceptable ads", i.e. corporations paying money to have their ads displayed anyway.
uBlock Origin is hands down the best ad blocker1 for browsers and one of the very few must-have browser extensions. The official GitHub repository is located under https://github.com/gorhill/uBlock2.
As an example, here is the set of rules I use to make YouTube a nicer experience. It will remove all recommendations, including those on your YouTube home page, and instead make the video use the entire width of the browser window.
! https://www.youtube.com
www.youtube.com###secondary
www.youtube.com##ytd-browse[page-subtype="home"] #primary
www.youtube.com##.ytp-show-tiles.ytp-endscreen-paginate.videowall-endscreen.ytp-player-content.html5-endscreen
You can also use it to apply CSS styles to specific websites. For example. add the following to your filters to force dark mode onto Hacker News3:
news.ycombinator.com##html:style(filter:invert(95%) hue-rotate(200deg); background: white)
I'm using the same filter for Wikipedia, but added another filter to prevent image colors from being inverted:
wikipedia.org##html:style(filter:invert(95%) hue-rotate(200deg); background: white)
wikipedia.org##img:style(filter:invert(1) hue-rotate(-200deg))
1 or "wide-spectrum content blocker" as Raymond Hill calls it
2 https://github.com/gorhill/uBlock
3 https://news.ycombinator.com/