ssh -L 5548:127.0.0.1:548 user@host

If the box you’re SSHing to is the machine you want to Appletalk to. Awesome. Otherwise change 127.0.0.1 to the name of the server you want to talk to as the remote machine sees it.

The initial 5548 part is a port on your machine that will become the gateway to the remote box. I chose 5548 because you don’t have to be root to bind to it and it’s moderately memorable. In the style of 8080. Anyway. To connect go to Finder and do Apple-K as normal. Then enter the URL afp://localhost:5548/. The SSH terminal session must be active for the forwarding to be open, unfortunately.