IRC wasn’t federated though, but you could indeed connect to multiple servers with the same client.
I mean
There were networks such as: EFnet Undernet Quakenet DALnet
different servers in different regions did network together.
There was a different word for ‘defederation’ back then: net split https://en.m.wikipedia.org/wiki/Netsplit
And it was usually from a networking issue.
I’m still salty that an IRCOP from a (now defunct) Canadian server used a net split as an attack: https://en.m.wikipedia.org/wiki/IRC_takeover
to steal a # channel from my friends and make it private long enough to sort out the bot auto bans. We appealed, but because they were an IRCOP, the other IRCOPs from the federated servers were just like, “whatever, pound sand users, go run a server if you want to control stuff like us.”
Anyway, IRC was a connection of various servers run by various people/corporations/universities etc.
Both Usenet and IRC are federated. Usenet started out as BBS synchronising their message boards, IRC literally means “internet relay chat”, and everyone who spent any amount of time on IRC will probably have witnessed a netsplit, where servers would desync for whatever reason.
AFAIK none of them had automatic/open federation though, that is, you couldn’t just spin up a server and connect to an existing network of servers, each was run by a clique of admins you’d have to talk to, first, and you’d be expected to serve clients that weren’t yourself.
