[LeEco Le Pro3 Questions & Answers] tsongming:
Follow these steps to completely unlock your bootloader, install Twrp and root. Do yourself a huge favor and make a full Twrp backup and save it to your PC. Enjoy your phone.

https://xdaforums.com/showpost.php?p=75009966

Edit those are X727 instructions, ( But you can still use the instruction above as a guide, you just don't need to flash a different bootloader.) But since you have a X720 it's a little easier.; use these instructions instead : https://www.skyneel.com/unlock-bootloader-leeco-le-pro3

Basic Instructions:

Download and Install ADB drivers and fastboot tools on your PC.

With EUI System Settings: Enable the USB debugging on your device after enabling ‘Developer Options’ by going to ‘About phone’ and tapping build number 7 times.

Usb debugging

On the PC : Open the ADB folder, located in C: Drive

While you are in the ADB Folder, press Control + Right mouse click” and choose “Open command window here.”

ADB COMMAND

Now connect your device to the PC using a USB data cable.

Boot your device into “Fastboot” ( hold volume down and power at same time) mode and give the following command : reboot bootloader

adb reboot bootloader

Execute the following command to unlock the bootloader.

Run "fastboot devices" to check that you can see your device

fastboot oem unlock

Run "fastboot oem unlock-go" to unlock your device temporarily

fastboot oem unlock-go

Run "fastboot oem device-info" to verify unlock status Unlock status should read true

That's it your device bootloader is unlocked.

Make sure adb can see your device when you run "adb devices"

Run "adb reboot bootloader"

Run "fastboot devices" to check that you can see your device

Run "fastboot oem unlock-go" to unlock your device temporarily

Run "fastboot oem device-info" to verify unlock status

Immediately flash Twrp and Magisk Root

2. Install Twrp :

https://twrp.me/leeco/leecolepro3.html

****** Scroll down to see: Fastboot Install Method

Reboot to recovery , checking boxes to install Tw4rp manager, if it appears.

When you are ready to install a Rom I highly recommend AICP 14. Go to that thread for assistance.

For future convenience I highly recommend that you buy an***OTG drive:***it makes the whole process a thousand times easier: Usb 3 drives are cheap usually somewhere near $5 and absolutely worth it

**Unlocking the Bootloader** Another option

* Mauronofrio created a tool called: "TOOL ALL IN ONE"" it's great, install it and check for updates.

Get it here: https://xdaforums.com/le-pro3/development/tool-tool-one-mauronofrio-t3580611

* The all is one tool is excellent and you can use it to install everything if wanted.

* I usually recommend it for novices that can use it to help with unlocking the bootloader and installing TWRP.

* The tool will also update your copy of ADB, android Drivers and provide system wide privileges for ADB

* It can unlock your bootloader, install TWRP and root and you can even use it for rom installation

**LETS RECAP :***Choose using the All in One Tool or the ADB Method*

***BEFORE DOING ANYTHING***

* Make sure you have enabled the developer tools,

* Turned on USB debugging

* Authorized your computer on your device I.E: “MTP”

* Make sure the All in One Tool can see your device* (*) Select your device from the drop down menu, then click check* (*) Choose to install drivers, and set ADB and fastboot privileges from advanced menu. (*) First attempt to unlock, then check bootloader status

* Next, choose Recovery flasher and manually select your copy of TWRP or download it through the tool

* After you have received the success message, I recommend doing the rest of the install manually within Twrp Recovery.

Worst case scenario, if you need help PM me, and I can help you remotely, note : I will charge you a fee.