It's very easy to discover and follow PeerTube accounts & channels from Mastodon:
1. Go to a PeerTube site (e.g. https://fedi.video )
2. On the account or channel you want to follow, click ⧉. This copies its Fediverse address.
3. Paste the Fediverse address into the search box in Mastodon etc. This makes the profile appear within Mastodon and you can just click "Follow".
To easily and safely discover high quality PeerTube stuff, have a look at https://fedi.video
Screenshot of what happens when you paste the PeerTube channel's Fediverse address into Mastodon etc. The profile of the PeerTube channel has appeared in the search results within Mastodon, and there is a follow button next to it which you can click to follow it from within Mastodon. If you can't see a follow button, click on the profile name to see its profile and click follow there.
Below the screenshot is a caption saying "Click Follow to follow the channel or account".
Screenshot of a PeerTube channel profile with the icon highlighted which copies the profile's Fediverse address. Below it is the caption "Click on the ⧉ (the copy icon), then paste it into search box in Mastodon etc to follow."