Greasy Fork is available in English.
Play videos and songs on the website via mpv-handler
This is easy, but it will destroy the video player on the page. (The video cannot be played before you refresh the page)
I will not change this. And you can close the page after opening mpv.
It would be nice if you could figure out how to terminate the video loading in YouTube once the icon is clicked. It successfully pauses the video, but it keeps loading in the background after mpv has opened.