I'm not a fan of either and would advocate everyone not consume large amounts of video content because of how heavy it is from an environmental point of view and move away from corporations from an anticapitalist/freedom point if view.
Let's not kid ourselves though, as shit as twitch is, it does not come close to having the same grip google has on the internet and our lives.
Peertube is a completely different platform, perhaps you're mixing it up with YouTube clients like newpipe or invidious?
How many people use Pornhub for discovery though? I usually find interesting content through a search engine, through word of mouth, through posts on here, etc. at which point it doesn't really matter where the porn is hosted. A lot of the useful content I use aren't even on Pornhub.
Seriously though, I agree with you, githubs value to open source is not it's discover-ability. Personally I think its value comes from the stability, as much as I'm an advocate for self-hosting I know from the amount of dead links on the internet that we could have lost a lot of projects or at least they would move about as hosts went down.
I quite like the idea of federated gitea, although technically there is already a federated platform for porn if you count Lemmy and/or mastadon.