I’m testing the free version of Gaea.
I’ve exported the mesh, which is quite dense.
I’m getting this result (the material doesn’t make any difference, the jagged lines appear even with the default material)
I applied the Shade Smooth, tweaked the auto-smooth and I’ve also tried Smooth Vertices to no avail.
Edit: For a moment I thought it was working but no, the jagged lines are still there.
Edit 2: Exporting quads and then adding a subd in Blender seems to address the issue.