fyi:
- https://github.com/yt-dlp/yt-dlp lets you download videos (from youtube and also hundreds of other sites)
- for desktop, https://mpv.io/ is free and lets you watch youtube (or any other video) at even more and faster speeds than youtube premium does, among many other features
- for android, https://newpipe.net/ lets you play youtube in the background (and download videos, and block ads, …)
- https://ublockorigin.com/ blocks ads everywhere (and yes it does still work on youtube, at least in firefox anyway)


AdGuard is also an acceptable option if you’re willing to pay a small amount. I won’t say it’s as good as ublock but it’s what I have to use on iOS to actually get good blocking.