Circular arcs in a feature layer with no z-values display as straight lines in ArcGIS Online.

Workaround

• In ArcGIS Pro, copy the curve features and paste them to another layer with z-values enabled and publish it to ArcGIS Online. The curves are displayed as expected. Refer to the documentation for instructions: How To: Copy specific line features and paste them to another layer in ArcGIS Pro.
• In ArcGIS Pro, convert the curve feature layer to a layer with z-values enabled using the Feature Class To Feature Class tool and publish it to ArcGIS Online. The curves are displayed as expected. Refer to the documentation for more information: ArcGIS Pro: Feature Class To Feature Class (Conversion).

Steps to Reproduce