just FYI - following some authorities on the official instance the press and information channel of the government (Supreme Federal Authority) joined as well. Yay.
Well, it is in german, ActivityPub would allow multiple languages, see Activity Streams 2.0 #naturalLanguageValues
The Press and Information Office of the Federal Government or in short Bundespresseamt (BPA), informs citizens and media at home about the work of the German Federal Government and informs the latter about the news situation in Germany and worldwide.