Shade Smooth not working in the render tab (even after recalculating/merging normals) This weird flat shading is occurring on the curved surface even after shading smooth and merging normals.
It is a model exported from Rhino as an FBX
No modifiers applied.
Viewport shading and edit mode visuals are provided below.
You need more subdivisions on the object to appear curved.
Here's an object only with smooth shading (rendered image on the right), note that the edges and faces are visible.

Here's the same object with smooth shading and a subdivision surface modifier. The curves are smooth.

Just for comparison, here's the same object with flat shading. Compare to smooth shading only.

Click on the images to show enlarged in full screen.