

I wouldn’t get too depressed about it, it would just be another niche bit of alt-tech if it were anything other than completely neutral. I can’t think of a case when an anti-left fork of a software was memorable as a self-hostable tool. The closest I can think of is Gab, which hardly qualifies, nor does it hold a torch to Mastodon.
This describes a general forum format, but you might mean chan imageboards specifically. There have been federated imageboards for a while, but they’re very niche and experimental and I don’t see the value. The two examples I’ve heard of are NNTPchan (2015-present, NNTP protocol) and Fchannel (ActivityPub protocol).
There’s the related imageboard webring, but there’s no actual federated interaction between the boards, it’s effectively just cross-advertising to allow easier discovery.