One thing that wasn't obvious to me initially when I started searching for !community@instance is that the search results are fetched asynchronously. So you might see "no search results" and think it failed, but if you let it sit there a bit, the results will often appear. Hitting the "Next" button sometimes helped too.
I was having a ton of difficulty with this initially following the documented steps and was getting a “404 community not found” issue for something I knew was on lemmy.world.
Convoluted so if anyone knows a better way please share (using mobile):
Tap the hamburger from your home server
Tap Communities
Enter minimally three characters and hit search (this should take you to a more robust search page)
Change the Communities drop down to All
Paste the url for the desired community and tap Search
Tap the community
Tap the sidebar and Subscribe
Don’t know why it doesn’t work the normal way or when the URL option is used. Only All worked for me.
Using the manual URL worked best I think. The other approach (!community@instance) never seemed to load.
I do have a follow up question though, why do these posts look so different on each instance? Do we only get new content going forward I suppose? The post itself is from before I subscribed so old posts seem to come in, I guess maybe not old comments though?
Yeah theres some shenanigans with the federation. Dont know what exactly causes it but probably something with other servers not federating fully with us yet due to not much interact between the two instances
Do you have any insight into the server's performance? I was getting some errors around the same time before I tried. Maybe it was just lag. That's basically what I tried (I think, maybe I got a small detail wrong). I'll try later and see.
The second link contains the probably the answer. If you did everything right with the search and your desired community still does not show up it might be because your instance defederated the other instance