I am using domains and subtypes with a feature class that is being edited in Collector. When exporting the collected data as a file geodatabase from AGOL, the subtypes are not retained. The result of the data when viewed in ArcMap is that I only see the subtype codes and not the descriptions. I have defaults set, which is likely the only reason any data shows up at all. Because subtypes only work with short or long integer field types, only codes will show up in the data if subtypes are stripped upon export. Anyone else using subtypes with AGOL and Collector?
My solution to this was to publish the data with my symbology displaying the field containing my subtypes. If the subtypes are symbolized it will keep the subtypes and associated domains.
Be careful though, if you change the symbology to another field you can still return to the subtypes field but it'll only display the codes not the descriptions for your subtypes. The associated domains will also be broken.