Well, that’s to be expected. Probably it’s the way panorama was shot. In engine, there is little you can do, since the panoramic image is static. Pawn and the sphere should be locked between each other - only movement allowed is the rotation of the camera.
You also could tweak FOV of the camera, to try and match panorama curvature. Standard 90 degrees usually works, but if panorama was shot with some special lens, it might be too or not enough curved.
CubeMaps are the different beast entirely, and that’s not what you need. It’s reserved for in-engine stuff used for static reflections, and it’s usually very small (like 512x256), and is in HDRI format.
You need a LongLat projection picture. It looks like that
If it looks different (like more straight vertical lines and no top/bottom, or a cross made from squares), you need to convert it to LongLat projection first. There is a shader command in material editor, that does that (Cylindrical to LongLat, or Cubemap to LongLat), or something like that. Not sure, though, if it works on non-HDR input. It’d be better to convert somewhere else, like modeling or postprocessing software (reproject using special camera). Less complex shaders you use on mobile, the better.
Why use LongLat? Well, it’s usually the most efficient way to pack panorama into 1:1 or 2:1 texture. Other methods have their uses, but not for this task.