Hi Jeffrey,
Survey123 for ArcGIS data is stored in Portal for ArcGIS behind-the-scenes as feature services. The feature service "lives" in the associated GIS Server that acts as the hosting server for Portal, and the actual feature data "lives" in the ArcGIS Data Store (not in an enterprise geodatabase).
So you could simply navigate to the survey's feature layer Item Details page > Overview tab and click Export Data.
Hope this helps,