At one point with Apple’s Continuity I had Gchat, Facebook messenger and SMS on a single window in my MacBook.
Yes, but with only a single xmpp account, that federated access to gchat, fb?
Yes, at one point I ran my own prosody jabber/xmpp server and regularly chatted through it with friends who were gchat users. Even had presence (idle , busy, etc) support! It worked amazingly.
First they killed federation, then they killed xmpp support entirely.