Just joined Lemmy today. From what I understand, there are different Lemmy instances that host different communities. I supposed that to interact in a community hosted in a certain instance, I would need to create an account for that instance. Ended up creating 10 different accounts.
I am on lemmy.one. Are you using jerboa? I posted a similar experience using jerboa and someone suggested logging in to the lemmy website instead and using the web search function to add communities not already connected. That totally works!
I have the same problem on both. Seems like the !name@server nor the full url ever populate. What I am finding is that after some time, if I come back and just type in a partial name (to search federated communities) it'll show up.