Wallpaper is distorted after setup on Galaxy Note9
This symptom is a temporary phenomenon that can be used as a normal screen by changing the wallpapermand this is not display problem. There are some errors in restoring backed up wallpapers from other devices via Samsung Cloud.
Samsung is scheduled to release a new Software update at earliest possible. Please check regularly for updates to your device SW via the Smart Switch PC or FOTA. Samsung encourages users to keep your software and apps updated to latest version.
Alternatively to change the background wallpaper, following the below steps.