SuperModel-UI v0.9.151
When you see the "network board not present" screen, enter the Test Menu by pressing the Test button (mapped to 6 by default).
Using the Service button (5 by default), navigate to "Game Assignments" and press Test to select. In the Game Assignments menu, change "Link ID" from "Master" to "Single".
It is saved to the NVRAM folder each time Supermodel exits and is re-loaded at start-up.
Save states will also save and overwrite NVRAM data. If you alter any machine settings, loading an earlier state will return them to their former configuration.