See screenshot. Example here is !privacyguides@lemmy.ml On lemmy.ml I can see several posts, on lemmy.world, none.
I logged in in both, I joined both, both profiles have enabled NSFW content and language is untouched (so all languages should be displayed).
What is the reason for that and how I get the posts on lemmy.world?
My guess:
Federation only starts when a user subscribes to a community. So no lemmy.world user has subscribes to it until now.
And there is no backfilling of post history. only new posts will be federated.
That's why it is empty.