Jabber was big with the "federated, decentralized" crowd. I recall several colleagues who established Jabber addresses and advertised them, sometimes as their only IM address.

XMPP was more than Gtalk, but I think that Gtalk was the "death knell" for XMPP, having absorbed it and sort of claimed it as their own. Anyone who would've used federated Jabber addresses in those days is using Mastodon now.