How to root Honor 9 lite? I have bought a new Huawei honor 9 lite and I want to root it.

Model No: LLD-L21
Android version: 8.0.0
Software build version: 8.0.0.123 (C185)

How can I do it?
To root your device you first need to unlock your bootloader, and Huawei no longer provides bootloader unlock codes. There are several possible options, but all of them are paid, ranging from €3 to $55 depending on your choice. 
I'm not affiliated with or responsible for any of the services mentioned below. 

Read unlock code from phone:
(Keep in mind that these methods are not guaranteed to work in Android 8.0.0 or newer, but if it doesn't work you can ask for a refund)

DC-Unlocker €3: You can buy 3 credits (one credit=one euro) from their website https://www.dc-unlocker.com, download the software for your PC and get the unlock code by connecting your phone to your PC. You can follow the tutorial in their website for a complete step-by-step.
HCU-Client €3: This is associated with DC-Unlocker but supports some newer devices, so it is generally recommended over DC-Unlocker. The website is https://hcu-client.com and you can follow the same steps above.

Order unlock code by IMEI:
(This method works for any version, but is more expensive)

Global Unlocking Solutions $20-$22: The website is https://global-unlocking-solutions.miiduu.com/bootloader-unlock-codes-choose-model-below .The website looks sketchy but plenty of XDA users have had success with them. The ordering process is straightforward.
FunkyHuawei $55: The website is https://www.unlockhuawei.com .The advantages of FunkyHuawei are: If it doesn't work you can ask for a refund, and they just have a very reliable track record.

You can just Google how to install ADB and Fastboot. There are plenty of guides. Also install Hisuite (for drivers) too.
After you order the code unlock the bootloader with fastboot oem unlock ******** (replace with the code, also that will WIPE ALL YOUR DATA)

Download TWRP from https://forum.xda-developers.com/9-lite/how-to/honor-9-lite-twrp-3-2-1-0-available-t3771358, rename it to twrp.img and to flash it use "fastboot flash recovery_ramdisk twrp.img".

Google "magisk xda download" and download the Magisk ZIP from the XDA thread. Boot into TWRP (You can Google how to do that in Huawei devices) and go to Install, and choose the ZIP you downloaded, and confirm, and you have rooted your Honor 9 Lite. 

So that is there to it. A lot of work and some money is needed, but there are no other choice for now.