Invidious [1] running on your own - or someone else's - server, no ads. Everywhere. You can also 'subscribe' to channels without telling Alphabet about your preferences and without giving them the possibility to 'accidentally' unsubscribe you which seems to be prevalent among some channels [2]. The interface is far lighter than the Youtube uses which makes it possible to watch videos on hardware which chokes out on the rich bouquet of Javascript found in the latter.

While you're at it you may as well add Nitter [3] to make (a read-only version but who wants to write on) Twitter more palatable and, again, light enough to not choke out less endowed hardware. For Reddit there is libreddit [4], again read-only.

These three are written in newish trendy languages and as such can also be used to evaluate their pro's and con's. Invidious is written in Crystal ("compiled Ruby", sort-of), Nitter in Nim (Python-like syntax, compiles/transpiles to C/C++/Javascript), libreddit in Rust (no introduction needed...).

[2] Since I do not have a Youtube/Google/Alphabet account and as such never tried to subscribe to anything I can't prove the veracity of this practice but I keep on hearing people complaining about their subscriptions disappearing

[3] https://github.com/zedeus/nitter

[4] https://github.com/spikecodes/libreddit