Ok, I managed to find it by doing the following. From the lemmy.eus post, click on the fediverse icon, which link to the same post on Reddthat : https://reddthat.com/post/1976 and from there, if I search for this url in lemmy.world, I find it in search result. But it is kind of confusing, why does the fediverse icon link to a reddthat post even though the post has been originaly posted on lemmy.ml?

I see the same posts now, even if the order is not exactly the same. I guess it may be some kind of synchronization issue as the servers are overloaded today.

Searching for the url in lemmy.world, I do not find the original post. I only find this actual post where the link is in the post text.

Moreover, I do not have any issue finding the community from the lemmy.world and subscribe to it but how can I find this specific post from there? If the post is not new or hot, it may be burried under all the more recent posts.