And to use it with a similar feature set, everyone is using different extensions which also have to be supported by the clients. I know there is this one server implementation (name escapes me at the moment) and Conversations on the client side, but it’s hardly the standard and we’re not really talking about plain XMPP then anymore.
The same is true if you use a Matrix server other than Synapse and a client other than Element. If fact these days the spec incompatibilities are way worse on Matrix than on XMPP.
And to use it with a similar feature set, everyone is using different extensions which also have to be supported by the clients. I know there is this one server implementation (name escapes me at the moment) and Conversations on the client side, but it’s hardly the standard and we’re not really talking about plain XMPP then anymore.
The same is true if you use a Matrix server other than Synapse and a client other than Element. If fact these days the spec incompatibilities are way worse on Matrix than on XMPP.