social.dk-libre.fr is a Fediverse instance that uses the ActivityPub protocol. In other words, users at this host can communicate with people that use software like Mastodon, Pleroma, Friendica, etc. all around the world.
This server runs the snac software and there is no automatic sign-up process.
Ah, the first details emerge. TL;DR: Denic experts are looking for the root cause.
"Frankfurt am Main, 5 May 2026 - DENIC eG is currently experiencing a disruption in its DNS service for .de domains. As a result, all DNSSEC-signed .de domains are currently affected in their reachability."
UPDATE: Seems to be fixed, all back to normal.
Oops. Seems that #Denic has b0rked DNSSEC for the .de TLD. They list an ongoing issue but no details are (yet) available. https://status.denic.de
UPDATE: Now upgraded to a service disruption, still no details.