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?
It could be because the admins are setting an amount of time to stop pulling old data. Or it could be the backfill issue. Mastodon had a similar backfill issue open as well, though that has been opened since 2016 and still hasn't been fixed.
The one you linked is an old one anyway, you should use !privacyguides@lemmy.one instead.