I've never used RabbitMQ, but NATS supports clustering, super clustering, and leaf node connections. I'm guessing the latter is the closest to what would be considered "federation" in this context.

Edit: spelling

NATS JetStream has equivalent functionality to federation out of the box with stream sourcing, combined with super-clustering and leaf-nodes. You can have streams that source and combine messages (with filters and subject transformation) from other sources and that sourcing happens in a 'guaranteed store and forward' manner, even if for example the stream being sourced is located in another cluster in a different region or provider or in an edge device (running a leaf node) that has only partial network connectivity (e.g. on a vehicle) and completely different security setup.

(for more detail check out this and the other YouTube videos on the Synadia channel https://youtu.be/WH55czo1BNk)