Here's the announcement I made back when PeerTube support was added, which includes links to every active channel i could find - https://piefed.social/post/126190
Join any of those groups and then new videos in those channels will appear on your home page. You can comment on and vote for those video posts just like any other post. You cannot create new posts in those groups!
In practice I've found this doesn't work great because none of those videos get enough upvotes to be visible in the home feed for long and most channels post videos quite rarely. But when more people subscribe or Lemmy gets PeerTube support this will change.
If there is a PeerTube channel you know of but which isn't added to PieFed yet, add it like you would a lemmy community: go to https://piefed.social/community/add_remote and put the address of it in. The channel https://tilvids.com/c/arthurpizza/videos would be typed as [[email protected]](/c/[email protected])