PeerTube resembles fedeproxy. More than mastodon because it does not deal just with conversations but uses ActivityPub for federation purposes.
A PeerTube server can follow other PeerTube servers and be notified whenever new videos become available. A fedeproxy server connects two software projects in the same way and one software project is notified when a commit shows in the other software project.
Here is the web interface PeerTube administrators can use to follow another PeerTube instance:
Each PeerTube instance is able to fetch video from other compatible servers it follows, in a process known as “federation”. Federation is implemented using the ActivityPub protocol, in order to leverage existing tools and be compatible with other services such as Mastodon, Pleroma and many more.
Federation in PeerTube is twofold: videos metadata are shared as activities for inter-server communication in what amounts to sharing parts of one’s database, and user interaction via comments which are compatible with the kind of activity textual platforms like Mastodon use.