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.
Yes, this is one of the most confusing thing to me about Lemmy right now. Trying to see content from Kbin on lemmy is very weird also. If I go to lemmy.world/c/tech@kbin.social, I can access the community but without any posts, and at the same time sh.itjust.works/c/tech@kbin.social gives a 404.