XMPP and IRC are great and all but a massive part of what people use Discord for is group voice calls with screen-sharing. I'm not sure what the alternative is for that. TeamSpeak is the closest I can think of but it's not a 1:1 replacement for a number of reasons.
it's possible to integrate jitsi in such a way that the chat has a function that will open a jitsi room and share the link to that. on irc this could be a bot. for people used to irc that's seamless enough. for something more convenient you'd want to integrate that feature into the chat client interface such that it can track who is in which jitsi room, etc...
