So, I have not tested a shipping build with Switchboard.
This is because the solution we need must be started via a different application. Thus, whatever command line switchboard uses, our other application will end up using.
Regardless, I have not attempted to go further with this as, from what I understand, a Development build that enables optimization is not too much different than a Shipping build.
If that is not true, please point me to what explains what the differences are. And if there is a lot of differences, it might be that Unreal 5.4 has a bug in nDisplay and we might try to migrate to UE 5.5.
But, I have never gotten a successful nDisplay configuration to work using UE 5.4 when compiled for Shipping. Not only does it seem to use the default viewport, it also never connects to other nodes configured for nDisplay (we have 2 nodes within our cluster configured in the .ndisplay file).