Alas not really watching a video on a browser.

If you use youtube-dlp to download the videos, it can use sponskrub to cut out those sections entirely (or flag them).

Android? Youtube vanced offers this built-in.

Never heard of YouTube Vanced. I see it's not open source. The feature list is interesting, but it doesn't say anything about tracking/telemetry. Does the app track you (and how much), independently of YouTube tracking?

I'm currently happy with NewPipe - which is essentially a youtube-dl GUI, and has to be updated just as often, which is damn annoying because FDroid is still completely broken UX-wise - but I have less tech-savvy people around me, who would very much like an alternative to the official YouTube app.

There's a NewPipe fork with SponsorBlock support. https://github.com/polymorphicshade/NewPipe

Newpipe works as well. Youtube vanced cannot be open source as it is just a nodded youtube client, which isn't open source. I cannot speak on tracking but I tracked its DNS requests and nothing out of the ordinary.

Need to check out vanced, NewPipe keeps breaking.

iOS/Mac OS X

Youtube-dl works on Mac, and you can get it working on iOS too. https://www.macstories.net/linked/downloading-youtube-videos...