There was a German social network a few years ago that did exactly that (before Facebook was available in German)

They had SchülerVZ for kids/teens, then they had StudiVZ for university students and finally they had MeinVZ for adults. The problem was, that they weren’t interconnected at all apart from the option to move your account to the next platform. So if you were just starting to study but you still had friends that were in school, you could’t keep in touch with them.

The German government already has their own mastodon instance on social.bund.de

Much better alternative to a EU funded social network, as this would automatically drive critics to the assumption, that politicians are controlling the narrative and deleting critical content. Also supports the development of open source and self hosted alternatives this way.