EDIT2: PeerTube is no longer using WebTorrent for Redundancy - see thread below
 
PeerTube has RSS feeds with WebTorrent links. You can grab those links and seed whatever content you wish using a WebTorrent client without having to install an entire PeerTube instance.

What does this do? It helps alleviate some of the streaming costs of servers and ensures a smoother experience for everyone on the decentralized web.

Yay for open source platforms!

webtorrent.io/desktop/

Thanks to several commenters, I was able to confirm that WebTorrent is no longer being used by PeerTube for redundancy.

The links to the torrent files still exist in version 6.x, and you can still peer to peer seed them, but it's not helping with server load when viewing videos on a PeerTube instance directly.

https://github.com/Chocobozzz/PeerTube/issues/5465

So what can you do to help? Watch a video and keep the page open. That's it. So you can't really help over time, but you can help in the moment.

If you are watching a video, you could be streaming chunks to another user, or vice versa. It's pretty unlikely to really help unless it's some type of viral video. Or maybe a live stream?

If you are an admin, you can follow a channel and pull in all of their videos. Doing so assists with redundancy, acting as a stream chunker for those videos.