Why can't I find federated communities on lemmy.one?

One of the things that has been frustrating me most deeply when trying to move to Lemmy, especially as the exodus from Reddit really picks up steam, is finding new communities as they set up shop. Most of them appear to be landing on lemmy.ml, which has adopted more of an open-door policy for community creation. That's fine, I'm not asking lemmy.one to necessarily do the same. I picked this instance to take some pressure off the really big ones.

But the process is maddening.

• I search for (e.g.) the string "no man" in my lemmy.one Communities page under "All". No results.
• Someone mentions a cross-federation search at lemme.de. Why isn't this everywhere?
• I search there for "no man" and two communities pop, one at lemme.ml and one at lemmy.world. There are no subscribe links.
• The lemmy.ml one looks popular, so I copy the full URL and put it in my lemmy.one search. No results, and no "no results" message.
• OK, so I visit https://lemmy.ml/c/nomanssky directly and click "Sidebar". Nothing happens. There appears to be a Javascript error preventing anything from working (including the hamburger menu). Is this because I'm a lemmy.one user?
• Start from lemmy.ml, and search their Communities for "no man", find the community, click through, click Sidebar. I get a magic string, [email protected].
• Back on lemmy.one, search for [email protected]. NO RESULTS.

I feel like I'm taking crazy pills! What is going on here?? Is lemmy.one blocking these instances? Can't be, I see lemmy.ml stuff all over. Starting to wonder if I just made the wrong choice and should go join the cool kids on a "big" instance.