Based on the provided source material, there is no information regarding a city named Ueli in South Sudan. The source identifies "Ueli" exclusively as a Swiss hypocoristic form of the masculine given name Ulrich.
The name is associated with various notable individuals from Switzerland, including athletes, politicians, and artists such as Ueli Bächli, Ueli Götsch, and Ueli Steck. No geographical data or municipal details for a location by this name are available in the text.