In this case, it's one specific channel: https://diode.zone/c/andybalaam_lectures/videos?s=1. That is, !andybalaam_lectures@diode.zone. It's run by @andybalaam@lemmy.ml / @andybalaam@mastodon.social
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?).
EG:
By comparison:
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.
I'm not sure that it ever quite worked - the videos currently on Lemmy are likely to ones brought in manually, rather than new ones that have come in via federation.
The community copies (on lemmy.ml, endlesstalk.org, etc) all show 0 subscribers. At a guess, it's because the format of the Followers collection on PeerTube is slightly different - it doesn't have the empty 'items' array that Lemmy expects, so it just rejects it. As such, any new posts will also get rejected by Lemmy (the same way it does if a community genuinely does have 0 subscribers). A couple of Updates have come through, so maybe Updates circumvent that check.
Well the one time I interacted from lemmy with comments it worked well: https://lemmy.ml/post/11677521?scrollToComments=true
So I figured federation was mostly sorted. Unfortunate to hear it’s still pretty rough.