[arielb1]

> PTYs are "terminal servers"—they're just sucky ones from a time when a terminal had fewer expected capabilities. But, indeed, you can connect a TTY directly to e.g. a serial modem, and then the person dialling your modem will get a TTY and login(8) will accept(2) on that descriptor and serve them a login prompt.

In a way, but ptys both don't do the "UI state" thing well, and don't do the "server" thing well - you can't really "take over" the controlling side of a pty easily.

> Now it was more like SSH was the terminal server, and screen/tmux was virtual desktops.

In the normal use of SSH+screen (`ssh -t foobaz screen -r`), SSH just tunnels the VT100-over-serial over the network, and provides the needed authentication and routing.