https://lemmy.ml/comment/524912

If an instance has not yet discovered a community on another instance, you have to use the search function to find it. I just did a search for “!vegan@lemmy.world” it showed up, and I clicked on the link. Now lemmy.ml knows about this community and the original link won’t 404.

It would be cool if we got a more useful message instead of a 404 though.