[Sony Xperia 5 III] Yeme:
First of all, Thanks to @johndaniel, @htcmage, @gorEisberg @Forbesii @morphvale @arjun_m4 for sharing all the information and files required for this guide.

FIRST THING FIRST: Data is priceless. Always backup before you modify your phone software.

Disclaimer: Not every carrier in the world support VoLTE or VoWiFi. Please ask your carrier first to get more info if you don't know if they provide support to VoLTE and 5G. Tested on a Xperia 5 III (XQ-BQ72).

Prerequisites:

* Xperia 1 III or Xperia 5 III (This guide works on Android 12 and 13)

* Windows Computer

* Firmware for your device

* USB Cable

Downloading Firmware​

Download XperiFirm from https://xperifirm.com/download/xperifirm-v4-6-0/ and Install

Open the XperiFirm and Download the firmware for your device ( check your model number and download the firmware)

Preparing the Device for Rooting ​

* Back up all the data from your device.

Make sure the device is supported for Bootloader unlock by opening the dialer and enter the code *#*#7378423#*#* and then press Service Info -> Configuration.

If the Bootloader unlock status is Yes, then you’re lucky and continue the rest of the guide.

Visit https://developer.sony.com/develop/open-devices/get-started/unlock-bootloader/ and Select your device and enter IMEI and get the code.

Enable Developer Options and then Enable OEM Unlocking and USB debugging on your device.

Download Platform tools for Windows using this link

https://dl.google.com/android/repository/platform-tools-latest-windows.zip

Open CMD and go to the Platform-tools directory and enter the below command:

adb reboot bootloader

Once it’s in bootloader mode or fastboot mode you will see blue light then type this command on CMD:

fastboot oem unlock 0xYOURKEY

Wait for the reply on cmd and then type

fastboot reboot

Now your device is Unlocked.

After reboot, configure your phone without entering Google Account's, we don't need this now, just connect your phone with a Wifi Network

Rooting​

Download and Install Magisk in your phone from here

In your computer, open the firmware folder you have downloaded and look for boot.sin file it looks something like boot_X-FLASH-ALL-4BA8.sin with around 96MB size (might look different for other versions and regions)

Download UnSin Exe from https://xdaforums.com/t/tool-unsin-sin-v3-v4-v5-unpacker-v1-13.3128106/ and then drag and drop the boot.sin this will give you boot.img

Rename the boot_X-FLASH-ALL-4BA8.img into boot.img (easier to flash) and then using Magisk Manager to patch it.

Just don’t delete the original boot.img we need that for the re-locking bootloader.

Now copy the magisk_patched.img into the Platform-tools folder and rename it into boot_magisk.img

Open CMD and go to the Platform-tools directory and enter the below command:

adb reboot bootloader

Once in fastboot mode type this command

fastboot flash boot boot_magisk.img

Wait for it and then type

fastboot reboot

After restarting your phone, open magisk and verify it's rooted.

How to extract your MBN files from your device's firmware​

After rooting your phone, you can use a file explorer (in my case I use Solid Explorer, you can download it from here if you want).

Select the folder root inside the app and then look for your .mbn files searching in this path:

root/vendor/firmware_mnt/modem_pr/mcfg/configs/mcfg_sw/generic/(area)/(operator)/Commercial/mcfg_sw.mbn

Copy your mbn file to a normal folder in your phone, like "downloads" and then copy that file again to your computer.

Enabling 5G and Volte​

Open CMD and go to the Platform-tools directory and enter the below command:

adb shell

su

setprop persist.usb.eng 1

Allow the access in Magisk after entering the su command.

If the phone, asks for Allow access press Deny.

Download QPST from https://qpsttool.com/ and install, also, you can find the Qualcomm Drivers inside the zip, install them.

After that, it should show up 3 Xperia on the device manager and install one by one manually using Qualcomm driver just youtube this part. Use Qualcomm USB diagnostic 9091 or 9081.

REMEMBER: To configure modem files in Efs explorer or flash the MBN file it is required to enter the following commands in adb:

adb devices (to start the usb debugging, allow your computer if is neccesary)

adb shell

su

setprop persist.usb.eng 1

Open QPST Configurator, check the list and find which COM port corresponds to "LAHAINA". Go to the device manager and disable the rest, ONLY KEEP THE PORT FOR LAHAINA. Quit any QPST tools after this.

Open command line in the EfsTools folder, type

./EfsTools.exe efsInfo

and press enter. No error should occur if you configured correctly, and the COM port in step 3 should be shown.

I attached some mbn files on this post, check if some of them are compatible with your carrier.

Select the mbn file from the mbn folder. Find the mbn file for your carrier. If you're using a secondary operator, please use the mbn file for the main operator (e.g. Telcel -> use ATT mbn). Copy the mcfg_sw.mbn to the root of the EfsTools folder, open a terminal inside this folder (shift + right click = open a new Powershell Window) then type.

./EfsTools.exe uploadDirectory -i mcfg_sw.mbn -o / -v

and press enter.

The program will overwrite your modem information updating it to the mbn file you flashed.

Open EFS Explorer and select LAHAINA if the name is there otherwise try one by one until you see a bunch of folders.

Once all the folders are showing up go to Policyman folder and copy carrier_policy.xml attached in this post and paste it there.

Restart the device.

You should now have the Speed of 5G or 4G+ and Volte enabled.

Don’t stop here.

Time to go back to Stock (Unroot) ​

Open CMD and go to the Platform-tools directory and enter the below command:

adb reboot bootloader

Remember the original boot.img we have before patching copy that file into platform tools and replace it with the patched boot_magisk.img

Then type this command:

fastboot flash boot boot.img

Once that’s done then type this command:

fastboot oem lock

Wait for the response and then type this command:

fastboot reboot

Once that’s done your device should format and bootloader locked and back to stock ROM with 5G and Volte enabled.

Enabling VOLTE Options after re-lock bootloader and unroot.​

Go to Playstore and install Shizuku app.

With the app opened, open up a terminal and write

Code:

adb shell sh /sdcard/Android/data/moe.shizuku.privileged.api/start.sh

to start it

Check the app. It should say Shizuku is running.

Download and install this apk

In your app drawer find Pixel IMS app, open it and click on allow all the time for "Allow Pixel IMS to access Shizuku"

Hit the enable VoLTE button at the lower left.

Go to settings, mobile data settings and you will find the enable Volte Option or 4G Call.

Also, it kept working after uninstalling Pixel IMS and Shizuku apps.

You can restart the device and the Volte/5G will remain active.

Type

*#*#4636#*#*

in the phone original dialler. Select Phone Information, press the dots at the upper-right corner and select IMS Status, you can check if the IMS status is registered.

Now, you can enjoy VoLTE, VoWiFi, and even 5G (depends on your carrier's support).

How to Update your phone keeping your flashed mbn and carrier policy files.​

Thanks to @bentree for the great idea, I just updated my phone with the firmware released today using newflasher and removing the modem files from the folder.

DON'T UPDATE USING OTA, download your most recent firmware with XperiFirm.

Download Newflasher (I'll attach the file on this post)

Extract the Newflasher files from the .rar file and copy them to the firmware's folder.

Remove the modem files from the folder, personally I removed these ones:

modem_X-FLASH-ALL-XXXX.sin

modemst1_X-FLASH-ALL-XXXX.sin

modemst2_X-FLASH-ALL-XXXX.sin

Open the NewFlasher.exe file and follow the steps in the command prompt.

Flash keeping your data.

After rebooting, your phone will boot as normal, but your will notice the Volte and VoWifi options are missed.

Repeat this step (Enabling VOLTE Options after re-lock bootloader and unroot).

Enjoy!