Surveys created in the Survey123 for ArcGIS website using drop-down choices display 'choice1, choice2, ...' when exported to a CSV, XLS or a shapefile.

Workaround

Download as a shapefile (shp), and use the Field Calculator to replace the values.

OR

Use Survey123 Connect for ArcGIS to create the survey instead of the website.

OR

Use the downloaded geodatabase feature class from Survey123 for ArcGIS and run the Table to Excel tool with the field alias and domain subtype enabled. All the correct values are exported to the table.

Steps to Reproduce