Greasy Fork is available in English.
I like to do a little trolling on youtube. This lets you keep adblocker on and simply replaces the video html with an iframe of it's own embed. Take that, Google!
< Rückmeldungen auf Youtube adblock replace with embed
It works correctly with normal videos, but you cannot see playlists (it jumps from video to video every 5 seconds), and you cannot see videos that are blocked on sites outside of YouTube. However, it is the best script of this class that I have seen so far, it delivers what it promises