Is there support for maps from Portal for ArcGIS inside the Configurable Map Viewer (CMV)?
If so, how should one reference a portal map?
CMV does not currently support the webmap specification (ArcGIS Online or Portal for ArcGIS). There are some efforts in progress to add that capability.
You can of course use your same ArcGIS Server REST services that are referenced in your portal webmap directly in CMV.