As far as I know, Jitsi uses SFU (i.e. not P2P, not MCU), so every device sends their stream once (to the server), which doesn't do any transcoding but only forwards the streams to each client.
Therefore (just like multicast) you only send your stream once, and every client receives n streams.
Therefore (just like multicast) you only send your stream once, and every client receives n streams.