There was a ActivityPub wiki clone, no idea where it got to.
The major upside of IA being built and owned by one central company is trust. We can (so far at least, if I'm wrong please correct me) trust IA to not censor/rewrite history. As soon as every man and his dog can contribute, that gets a lot harder to guarantee.
Edit: https://github.com/Nutomic/ibis
Don't take me linking it as endorsement, I think federated wiki's for anything other than fandom stuff to be madness.