I couldn’t get it work either but figured it was some authorized fetch stuff going on. What do you mean by channel string?
I see. I don’t know much about authorized fetch, I’ll have to investigate a bit (I’m able to follow the linked account from mastodon however).
I was able to find greg_channel@flipboard.video on this instance for example, a wild guess was that maybe lemmy expects peertube « communities » to have the « channel » string in the name but it’s unlikely 😂