HTC devices have a security system which is either S-ON or S-OFF. The S stands for security, so it's effectively Security-ON vs Security-OFF. Bootloader unlock is separate to S-ON/S-OFF. With S-ON, any system modifications you make to your device in certain protected areas are reset after a reboot.  When unlocking officially via HTC, only three partitions are unlocked. These partitions are boot, system and recovery. S-OFF is handy for tinkerers since it allows a few things that cannot be accomplished otherwise. Those include switching your device to another region, where newer updates might be available, as well as downgrading your firmware version should you have issues or find yourself needing to go back to stock. Having S-OFF also allows users to reset their Tampered flag to hide the fact that the device has been unlocked, although that has limited appeal since HTC is still required to unlock the bootloader in the first place. Users have been eagerly awaiting an HTC U11 S-OFF. On the HTC M8, S-OFF meant users could convert their devices to a Google Play Edition ROM, and even receive the OTA updates from Google. It provides plenty of opportunities and unlocks full control over your device.

The devs behind SunShine, a popular paid S-OFF tool for HTC devices have released an update which supports the HTC U11. At a cost of $25, you may regard it as expensive, but it's worth it for an easy S-OFF solution. Note, the S-OFF flag is not permanent. If you reboot, S-ON is re-enabled. All modifications (except for custom hboot/aboot) should stick, however, so you just need to make sure before you make any changes to the system that you run SunShine again. Jcase, an XDA-Member and one of the developers of SunShine, has promised all those using the temporary S-OFF will be upgraded for free if a permanent solution is released. It is unlikely for any other devs to unlock S-OFF as well, as on recent HTC devices the only supported method of unlocking S-OFF has been SunShine. The only exception to this has been Moonshine for the HTC M7, but after that device, SunShine has been required.

SunShine has added HTC U11 S-OFF Support

With this, users should start to see custom firmware and other new goodies populating our HTC U11 forums very soon.