IDK, XMPP group chats have always "jest werked" for me (though admittedly I haven't used them much).
The difference between XMPP group chats and Matrix group chats is that Matrix servers replicate all the message history, whereas XMPP group chats are hosted on a single server. IMO the "bring your own account to a central server" model of XMPP is a good thing, but the "replicate all the things" model of Matrix is not.
The difference between XMPP group chats and Matrix group chats is that Matrix servers replicate all the message history, whereas XMPP group chats are hosted on a single server. IMO the "bring your own account to a central server" model of XMPP is a good thing, but the "replicate all the things" model of Matrix is not.