So I have Nomad set to sACN as Default, Priority 100. Vision DMX Provider is set to sACN. on Nomad sACN Output Viewer sees the Mac as the Source.
On one machine it is working, and the other it is not. The screenshot is from the iMac that is not working.
One thing that would be nice to clear up is that it seems that for this software pairing to work the computer needs to be connected to a network. It would be great if it didn't, or if there was a loopback virtual network interface that would redirect the sACN output directly to Vision.