GNU Social.

One of the oldest decentralised social networks, part of the GNU project

Facts

Akkoma
Fork of Pleroma with extra features for federated social networks
DE · open-source
↗
BookWyrm
Federated social network for tracking and discussing books
DE · open-source
↗
Firefish
Misskey fork with improved interface for the Fediverse
DE · open-source
↗
Diaspora
Decentralised social network with focus on privacy and data ownership
DE · open-source
↗
Friendica
Decentralised social network with support for diverse protocols
DE · open-source
↗
GoToSocial
Lightweight ActivityPub server written in Go for social networks
DE · open-source
↗
Hubzilla
Decentralised platform for social networks, cloud and web publishing
DE · open-source
↗
Lemmy (EU-host)
Federated community platform; hostable in EU
EU · open-source
↗