I've never used it but Matrix does seem to support conference calls, if not natively then via Jitsi. I'm sure a good app can paper over the differences to get a voice-chanel out of it if this is what people are after, though I've never really used this much on Discord.
The same can be said of space-room vs server-channel. Of course a space has different semantics, the space doesn't own the rooms, etc. But they can be made to be nearly the same for an end user. In general organization of resources is much looser and less opinionated on Matrix. But an opinionated app can also paper over this to force a stricter hierarchy, while offering advanced users the ability to make their own spaces, etc.
The same can be said of space-room vs server-channel. Of course a space has different semantics, the space doesn't own the rooms, etc. But they can be made to be nearly the same for an end user. In general organization of resources is much looser and less opinionated on Matrix. But an opinionated app can also paper over this to force a stricter hierarchy, while offering advanced users the ability to make their own spaces, etc.