Explored it a lot. Just like with data export protocols, decentralised federation protocols are very fragmented. There are at least 8 major ones and everyone is pulling the blanket. We actually built an early prototype based on PubSubHubbub spec about 10 years ago and same thing happened - nobody wants to agree on a spec and federations are siloed. UNA is meant to allow flexible schemas too, so adopting any one social protocol would mean forcing fixed architecture that may or may not survive. It’s possible that there will be a clear standard at some point, but as of now - we’re watching.