Correct me if I'm wrong, but if I was on a different peertube instance, there'd be no way to discover his videos aside from word-of-mouth? As in, peertube has no global search, right?
There is offering from the creators of Peertube I believe: https://sepiasearch.org/. I think instances have to be added manually into the index, and tbh I don't use it much and so I'm not sure of the quality. But it sort of covers what you're asking for, at least kinda.