lemm.ee has shut down at 00:14 UTC.
unfortunately I realized too late that I have had hundreds of saved links to posts and comments from there, so I did not have enough time to save them, but anyways it is interesting that maybe a third of the post links I could try were dead. I think linkrot is happening much faster here than on reddit, even if just counting deleted posts.
$ curl -sI https://lemm.ee/ | grep '^location:' location: https://join-lemmy.org/