I think it's better to replace "server" with "coordinator" in that.
Just listening to the optech recap podcast 355, fyi nostr:nprofile1qqsgz07wf388du08kn6xj7l3qv9fpudqk7plrp7n9xqq5nwcd9lewkgpzdmhxue69uhhwmm59e6hg7r09ehkuef0492279, joinmarket has a server to coordinate the coinjoin: the taker, the nuance is that there is an open market for who can run this server.
The only truly decentralized coinjoin protocol is coinshuffle (++), but it's very complex and I think was never implemented.
Discussion
Valid point!
In fact the makers are usually running on a server (ie always online machine), while the takers can come online only for this round.