Back in the day if you wanted to root or rom your HTC device you would need to use a tool like SunShine to turn off the security feature and obtain S-OFF status. SunShine still provides S-OFF status for most HTC devices, and can even bootloader unlock Motorola devices. With S-OFF on the Sprint HTC U11 you can unlock the SIM and use the phone as a factory unlocked device.
In the past you could only use Sprint devices on CDMA networks. The U11 actually supports all networks including GSM once unlocked. To achieve this all you need to do is change the CID and then flash the unlocked RUU. Head to the link below for the appropriate links and full instructions.
via XDA