I have the game installed and working great in Wine, but when I try multiplayer it tries to connect, but then just drops me back to the menu. This is with directplay installed.

Any suggestions?

Did you look here already? https://www.gog.com/forum/general/the_judas_does_this_run_in_wine_thread_v1173 or here: https://www.winehq.org/search?q=smac

Maybe try the Linux sticky thread in general discussions.