If you put the entire url into the community search, I'll show no results at first, but either after about 5 seconds, or after clicking next, it should show up for you to subscribe to from whichever instance you're on.
Hi there! Looks like you linked to a Lemmy community using a URL instead of its name, which doesn't work well for people on different instances. Try fixing it like this: !twosentencehorror@sh.itjust.works