How to change UUID in ble app uart. I am using Nrf52832 and SDK 13.
Of course, your device will then not be recognised by anything that expects the NUS.
Have you studied the tutorials on setting up custom Services & Characteristics?
https://devzone.nordicsemi.com/nordic/short-range-guides/b/bluetooth-low-energy/posts/ble-services-a-beginners-tutorial
