Yes, it’s a client. Well, for better or for worse, no chance that this huge of a user base will move to piped. I don’t understand why it’s not super famous yet, but I guess invidious and piped are simply fringe tech still.
That’s why I said that YouTube would need a major tragedy to get a real hit, real alternatives like Peertube are going to struggle a lot against the network effect. Nebula has a much better shot given the amount of content creators invested on it, and it’s still a long shot.