AFAICT, federation hasn't been working from this channel to lemmy for ~3 months, for all the instances I checked (perhaps a particular lemmy version broke things?).
I'm not following anything else on peertube so I don't know how common this is (and I couldn't find anything on the GitHub issues), but different behaviour on mastodon and lemmy would superficially indicate that it's a lemmy problem, which would be a shame given that lemmy is much better for consuming peertube.