[LG V40 Guides, News, & Discussion] con_ritmo:
ATT v405ua30c on Android 10c.

I just did the bootloader unlock/twrp/magisk root.

It was a PITA because I ran into several issues (some of which I read about in this and other threads).

Things I encountered:

QFIL would not work on some of my computers (sahara error).

Fastboot mode on the phone would NOT work with some of my computers (the fastboot screen would appear and the phone would instantly reboot out of it).

I could NOT for the life of me get my computers to recognize my phone in fastboot mode.

The answer was to install a specific driver posted somewhere else on XDA.

In the end I used 1 computer for QFIL and another computer for FASTBOOT flashing. Really lame, but that's what ended up working.

Here are the exact steps I used...sorry it's poor formatting but all the steps (I think) are present:

What's Needed for QFIL:

[GUIDE] Unlock your LG V40 via 9008 mode (Every Variant except T-Mobile)

This Guide will explain how to unlock your LG V40 (Every variant except T-Mobile) Unlock Prerequisites: Make sure you have "Enable OEM Unlock" enabled in developer options, along with adb debugging. Very important. You'll be stuck with the red...

xdaforums.com

v35eng.img

prog_ufs_firehose_Sdm845_lge.elf

QPST for QFIL located at: https://drive.google.com/open?id=1Kx7OJoj7BZUJC7W-Bzxp7poKcAQgKPSI

Install QPST.

Run QFIL (admin mode needed?).

Connect phone to USB.

Phone is on.

Hold Power+Volume Down+Volume Up. When phone shuts off and blanks out screen immediately

start tapping on Volume Up. Keep on holding Power+Volume Down.

If phone doesnt reboot and screen stays black...you are in EDL mode...release all buttons.

You want to find Qualcomm HS-USB QDLoader 9008 listed in either windows device manager or in Qfil.

If it isn't listed you may have to "update driver" in device manager (I didn't have to)

A. QFIL BACKUP and V35eng flash

In QFIL select port: Select the highlighted Qualcomm HS-USB QDLoader 9008 port.

Change Storage Type to UFS.

Go to Tools->Partition Manager.

Click: Flat build.

Under Programmer Path load: prog_ufs_firehose_Sdm845_lge.elf

You need to back up the following:

abl_a

abl_b

boot_a

boot_b

laf_a

laf_b

You do it by right click-> Manage Partition Data -> Read for each entry. Find where they are saved and rename them to:

abl_a

abl_b

boot_a

boot_b

laf_a

laf_b

Once it is backed up:

Load v35eng.img to abl_a

Load v35eng.img to abl_b

Erase laf_a

Erase laf_b

If you get sahara error, reboot computer and phone and try again.

B. FASTBOOT UNLOCK

Now you you go to fastboot mode.

Turn off phone. Unplug phone. Hold down volume down and plug in the usb. Fastboot mode shows some info and you can cycle through

some colorful options with the volume keys (not needed)...and select with power (not needed).

Now you may Windows Device Manager an unknown Android Device in "Other Devices"

Go to:

https://xdaforums.com/t/guide-v20-fastboot-access-in-windows.3491439/

Download:

CT_HsPhone_General_Drivers.rar

These are the working FASTBOOT drivers. Install and reboot.

If you are connected phone will show up as an ADB->FASTBOOT device in windows Device Manager.

Bring up a command (cmd) prompt in Windows:

fastboot getvar all (to see you if you are connected and if you are booting from A or B)

fastboot oem unlock

fastboot --set-active=a (if it's set to B)

fastboot flash abl_a c:\original boot file here\abl_a.img (to put back the old bootloader once you ran the unlock command)

fastboot flash abl_b c:\original boot file here\abl_b.img

C. TWRP and Magisk Root

Go to:

https://xdaforums.com/t/twrp-lg-v40-judypn.3970111/

Get:

judypn_TWRP_bootable-metadata.img

drive.google.com

twrp-installer-3.4.0-0-judypn.zip

drive.google.com

This will be:

judypn_TWRP_bootable-metadata.img

twrp-installer-3.4.0-0-judypn.zip

Save twrp-installer-3.4.0-0-judypn.zip onto a microsd card.

Put microsd card into phone.

Go back to fastboot mode and type:

fastboot boot judypn_TWRP_bootable-metadata.img

TWRP will boot up on your phone.

Mount your sdcard and Install twrp-installer-3.4.0-0-judypn.zip

Go back to QFIL:

Backup boot_a which is now your Boot file with TWRP.

Copy this file to your phone microsd storage.

Install Magisk v23 apk onto your phone from:

Downloading Magisk App... | Magisk Manager

The download will automatically start in 5 seconds, please click here to access the download URL directly. If you are confused and want to know how to install the Magisk Manager on your phone you can click here.

magiskmanager.com

Run Magisk. Click install and patch your backup Boot file with TWRP.

Copy the Magisk patched file to your computer.

Go back to QFIL:

Load boot_a with your Magisk patched boot file.

Run Magisk...go to settings and enable Magiskhide.

Check Safetynet to make sure all is well.

Done!!!