What some people call "Fediverse" is actually just social media platforms speaking ActivityPub to each other:
ActivityPub's symbol consists of highly stylized letters "A" and "P" formed by four disconnected shapes arranged in an axonometric grid. It brings order and direction to a number of actually disconnected parts, just like the protocol.
The color choice of bold pink paired with plain gray aims to reflect the neutrality of the technology on the one side, but also the punk attitude to stick it to big tech social silos on the other side.
Letters in the logotype are set in PT Sans Narrow (SIL), a free font of course.