sub.rehab would have me believe lemdro.id/c/android is the main/biggest successor. lemmy.world isn't even mentioned, ".ml" looks like it's the 2nd biggest.
Searching within .world gives all 3 results but the number of subscribers in lemdro.id and .ml are way under reported.
Searching on feddit lemdro.id and .ml don't even come up.
For any given topic/interest, I could end up in a dead community while thinking it's the main place, depending on which search I use.
It's really frustrating to find communities this way. And I don't want to add 3+ communities that are the topic because I'll end up sometimes having the same article posted 3 times in my feed.
Secondly... Links to other instances
So in the guide by amirzaidi, it says take the link you've been sent and paste it into the search bar. But I've tried this with a random post from .ml and lemmy.world came back with nothing.
I could manually change the url and append it to the end of lemmy.world but that's not a good longterm solution. Maybe someone will build a browser extension that intercepts that url from another instance but the dev would have to keep on top of every time someone spins up a new instance.
I think the "big picture" idea of federated social media/reddit alternative is great, but in practice is seems too fragmented to actually work in a usable way for most people. I'm relatively tech savvy and will give it a solid few months while inital growing pains are worked out, but as it is at the moment I just don't know if I can see it taking off. In fact the only way I can really see it working for the masses is if one instance gets so big it "becomes" lemmy for most.
1(a) These are not the best tools to find communities. I believe sub.rehab is curated rather than being a full Lemmy community search tool (i.e. good for finding the few official migrations)
For example, you can use this search to find Android communities
If you set your instance using the home icon, any links will open on your instance so you can subscribe to them correctly
It shows similar subscribers counts etc to your first two searches, because it is an independent tool, while searching from your instance (lemmy.world) will only show what that instance can see i.e. communities and subscribers from federated instances
1(b) Each of these are different communities, with different content, moderation, and members. Sometimes there will be duplicate content and cross-posting. If you think they are so similar that the duplication is annoying, just pick one, otherwise subscribe to both
I understand that the way cross-posting is presented is being worked on for future Lemmy releases, but honestly duplication is not that bad at the moment except during large news events
2 Where are you getting links to Lemmy content that you are trying to open? Once you have subscribed to communities of interest, you may come across links to other communities in that content. There are bots that often 'correct' instance naming in Lemmy content to use the ! notation, so as long as you don't block them you'll get clickable links
Otherwise, yes it is currently the case that /c formatted links will need to be changed to your instance or ! formatted - I'm not aware of an extension to do so, but I presume some of the apps and front-ends will do this for you
Both yourself and AlmightySnoo above have recommended lemmyverse.net to find communities. I'll give it a shot. What's funny is that I found all the sites I mentioned in the Sticky post on Lemmy. So much for trying to learn before asking!
2 Where are you getting links to Lemmy content that you are trying to open?
The one I used in my example I just picked a random post. I have been sent links in a message by a friend who switched from reddit earlier than me.