ff2mpv (for Windows) v1.15
This extension is a fork of ff2mpv by yossarian. It aims to make it easier to send videos from Firefox to the mpv player on Windows. A native client is not needed. But the ytdl:// protocol must to be added to the registry for it to work.
Instructions: https://github.com/eastmarch/ff2mpv
Be sure to have both mpv and yt-dlp stored in the same folder.