[P8lite General] oziboy:
Disclaimer:

I am not responsible for what you do to your device, I tested these things for myself and posted it from my own experience, if you point the finger at me for whatever happens to your device, I will laugh at you.

HOWEVER, I am willing to help as long as it is asked kindly, and provided me with enough information.

Requirements:

Huawei P8 Lite ALE-L21 (DUAL-SIM)

5.0 Firmware of choice

Unlocked bootloader

Patience

Correct drivers

SD card of atleast 8 GB

Drivers: Install these before even starting!

Minimal ADB Fastboot drivers

Huawei HiSuite

Kingoroot Windows

TWRP 3.0.2.0 Kirin variant

Preparing environment: Making sure no admin priveledge is necessary

Install all drivers mentioned above in their standard directories, don't change anything.

Go to the following path:

For x64 OS:
C:\Program Files (x86)\Minimal ADB and Fastboot
For x86_32 OS:
C:\Program Files\Minimal ADB and Fastboot

Copy these files:

adb.exe
AdbWinApi.dll
AdbWinUsbApi.dll
fastboot.exe

And paste them on the desktop, in a folder called "rootingtools" so you're easily able to find it.

Then, go to your phone and enable USB debugging mode by going to

settings - about phone - press Build number 7 times

settings - developer options - USB debugging

Copy the content of "TWRP-3.0.0-2_P8-lite_KIRIN_variant.zip" and paste it into the "rootingtools" folder.

Backing up: Even though the unlocking process is not going to wipe your data, atleast it didn't for me, make SURE you have everything that you need backed up from the phone's internal memory.

Backing up your SD card wouldn't hurt neither.

First things first, unlock your bootloader!

I used this: https://emui.huawei.com/en/plugin.php?id=unlock&mod=detail

What you do is: fill in everything correctly and get the number at the end. It should be something in the words of:

Your unlocking password is: XXXX XXXX XXXX XXXX

(X resembles numbers, 16 numbers in total)

Copy the 16 numbers and go to the "rootingtools" folder on your desktop.

Hold the SHIFT key and right click inside the folder, then press "open command window here"

Now take your phone, power it off and power it on by holding volume DOWN and POWER.

You will get a white screen that says something like fastboot, and an android logo.

Plug your phone into the PC via USB cable.

In the command window write:

fastboot.exe oem unlock UNLOCKKEY

Where UNLOCKKEY represents the key you just copied, right clicking pastes the key in the command window.

It should return finished, so now your phone should be unlocked!

If you look at the screen, there will be text beneath the green Android logo saying "unlocked".

In this case, the operation has succeeded and you can go to the next step, else you can try again or post a reply.

Now write:

fastboot.exe reboot

Now the phone will boot up like normal.

Close the command window.

Android 5.0:

If your android version right now is Android 5.0, and you actually WANT to root 5.0 or anything below 6.0 you can proceed with this step, if you have 6.0 or want to root 6.0, skip this step.

Since your android version is 5.0 you're blessed!

You can easily root, but before proceeding you might want to make a backup

Make sure you have about 8GB of free storage either on an SD card or internal memory first.

Connect your phone to your PC in the booted-up state where you can see the homescreen, making sure that USB debugging is enabled.

Shift + right click inside the rootingtools folder to open a command window and write:

adb.exe reboot-bootloader

Your phone will reboot into the bootloader, a white screen with a green Android logo that says "unlocked" beneath it.

Now on the command window write:

fastboot.exe flash recovery recovery.img

Wait for it to finish and pull out the USB cable so it is NOT attached.

Power off the device by holding the power button, and power up by pressing volume UP + POWER.

Keep holding volume up until you see the Team Win logo.

Just slide the slider to the right.

Now go to "backup" and check every partition available.

In "name" you write:

MainBackupURTD

Then, go to the "options" tab and enable compression.

Go back to the "backup" tab and press "select storage".

From here you can choose where to back your data up, whether it be the internal storage or external SD card.

Press OK and swipe the slider to the right to start backing up.

Plug your phone in to make sure it doesn't power off during backing up, this process takes a while and you should let it do its thing.

When done, press "reboot system", your phone will reboot.

Let it fully start up.

Then, run Kingoroot on your PC.

Meanwhile, download the "SuperSU" app from the Play store.

Press the big "ROOT" button in Kingoroot and press "cancel" on every app your phone tries to install.

That way you will not install Kingoroot but SuperSU.

It will say "succeeded".

Now you can go on your phone and open the SuperSU app.

It will ask for an upgrade, press OK and go further with the normal installation (not the TWRP/CWM installation).

Let it do its thing and restart your phone.

Install any root checker and see if you're rooted!

Android 6.0:

Firmware version B188 or higher, below B524/B535 (excluding B524/B535):

Upgrade firmware to this one: LINK (Link fixed)

Installation instructions: place file to the "dload" folder in your SD card or internal storage, then go to settings - updates - menu - local update and press the update.zip.

Then, follow the guide reported here: http://rootmygalaxy.net/root-huawei-p8-lite-android-marshmallow-6-0-update/

Enabling Gyro sensor (rooted android 6.0, B524/B535 firmware only! ( sorry :[ ) ):

Download attached file.

Put attached file to SD card.

Open ES file explorer, swipe to the right, enable root browser and click the R/W tab, then set /system as RW.

Then copy the attached file.

Paste the attached file in /system/etc/permissions

Press the search button and search for "gyro" without quotation marks.

Long press the only file that's there - menu and press properties.

Then change the permissions to 644, it should look like this O represents off, X represents on;

X X O

X O O

X O O

Set UID is off, Set GID is off, Sticky bit is off.

Reboot phone and download "Sensor box for Android" on the Play store and enjoy your gyroscope!

Now you can use Google Cardboard, though you have to install the APK...

You can watch 360 videos on youtube too.