EDIT (2023-07-31T22:18:52Z): I have realized that I was not clear in my original intent for this post – it could be interepereted to mean that I am asking whether or not you could access, for example, Lemmy through the Tor browser. This is not what I meant. What I was more alluding to was if it were possible to create a sort of “hidden fediverse” that was separate from the fediverse over the clearnet. There exitsts, already, Dark Web forums, like Dread, and I wonder if those would benefit more from being federated – Lemmy seems like a good candidate for this.
Title changes: Added “More specifically, could one make a sort of “Hidden Fediverse”?”
ActivityPub isn’t anything more than JSON over HTTP(s); there’s no reason at all that you couldn’t simply tunnel all the traffic using hidden services over Tor using nothing more than the Tor daemon to create a hidden service and the proxy functionality to route all outbound HTTP traffic over Tor.