Edit: Fixed links for desktop, no idea if it works the same for mobile apps
Write it like [/c/sublemmy@lemmy.server](/c/sublemmy@lemmy.server) and it will link correctly. If it's giving you a 404 error just wait a minute and try again, the server needs to download the sub first
No not at all. Just try pasting https://lemmy.ml/c/piracynews Into the search page. It should bring up a link to the community in the search results, maybe immediately if someone from dbzer0.com has already subscribed there, if not it might take a few seconds. You should be able to follow the link in search and subscribe in the sidebar once you get there.
On Lemmy they call them communities, same for other Fediverse software like Kbin and Mastadon. I like Lemmy because it's most "Reddit like", but Mastadon is more mature and slicker. It resembles Twitter more.
It's the move of the piracy sub from Reddit that pushed me over to Lemmy. I'm really glad it gave me the push to do it. Had Lemmy bookmarked for a long time, but never motivated on it.
I have interest in other communities as well. There's a pretty healthy set on the Fediverse. Here's a site that's helpful in finding them on Lemmy; https://lemmyverse.net
I'm still working on adding communites and getting used to the interface so I don't have any suggestions, but it doesn't seem there's a lack of active content there.