Some complexity with this. First off, you have to be logged in. I also used the full URL convention when searching, putting in "https://feddit.rocks/c/piped" as what to search for. Now lemmy.world link you shared works.

EDIT I used the other convetnion, "!piped@feddit.rocks" on Beehaw and was able to get discover and first subscriber/join too.

Hi there! Looks like you linked to a Lemmy community using an URL instead of its name, which doesn't work well for people on different instances. Try fixing it like this: !piped@feddit.rocks, !piped@feddit.rocks, !piped@feddit.rocks, !piped@feddit.rocks, !piped@feddit.rocks