I wanted to join the history memes community which is in lemmy.ml but I’m on lemmy.fmhy.ml. For the other communities I would just search it up and join but it doesn’t show up in search. How would I join it then?
lemmy.ml is either down or extremely unstable right now. It's having trouble keeping up with the demand, and it isn't sending posts to federated servers. I say wait until tomorrow.
Sometimes search is a little slow. I’ve had to wait 5-10 seconds for the community search results to finally show up. Perhaps that is what you are experiencing?
I guess it has something to do with how active the community is. I had the same issue, and was trying to troubleshoot with Ruud why this happens. Today in the morning, my community started being more active and started to appear on other instances.
Make some posts in the community (and comments), invite users and after 24h, it should be visible to other instances as well. Could be a bug (because Lemmy is riddled with bugs).
FYI: I believe the lemmy.world community (this one) is for discussions specifically about the lemmy.world instance. You're from lemmy.fmhy.ml, which is a different instance.