In the list of instances, some of them are actually PeerTube instances. I didn’t look at all of the instances but two examples I saw were framatube.org and h3h3.club.
That’s a list of all the instances we’ve federated with, which includes some peertube instances.
There’s no association in the people making it (as far as I can tell) but they are both federated softwares using the ActivityPub protocol, like Mastodon, Pleroma, Friendica, others and PeerTube. “Fediverse” is a collective term used for all the sites on these interacting softwares.
I don’t actually know how Lemmy and PeerTube can currently interact (are any posts visible between the two? Can you use one account to vote on both of them?), but as Dessalines explained, lemmy.ml is already able to federate with them.
