Publishing a layer with a unique value renderer (symbology) to ArcGIS Online causes the values to be shown as domains.

Workaround

1. Publish the layer with the default symbology to ArcGIS Online.
2. Use unique symbology in Map Viewer. (In-house field name: Type)
3. Changes to unique values in ArcGIS Pro will not be added as a domain type in ArcGIS Online after applying the unique type of symbology in Map Viewer.
4. In the ArcGIS Online Data tab, it is possible to change the attribute values in the text form instead of a drop-down option.

Steps to Reproduce