A note on all, all only shows you what’s been fetched by your instance so far. So if no one in your instance has searched for community “x” you will not see any posts in all for community “x.” If you know about community “x” you can go into the search on the web browser and search community “X’s” direct link like https://lemmy.instance/c/x and search it twice and it will pop up and be a community that your instance connects with.
This is all changing pretty fast as both Lemmy and Lemmy apps update so, the way to do this will probably change pretty quickly. I do believe you can follow some links like !communityx@lemmy.instance now and it should work most of the time.
No problem, it took me a hot minute to figure it out! I was like “is this all there really is?”