Flashing Xperia 1 III

2022-05-17

Lineage isn’t officially available for the Xperia 1 III yet, but there is a build on the XDA forums that works great.

However, the steps to unlock the bootloader, flash the right things in the right places, and finally sideload gapps is a little scattered, so here’s how it’s done.

Bootloader

The bootloader is locked by default, but unlockable with a code you get from Sony itself, based on your IMEI number.

Boot into stock:

Enable developer mode
Make sure "OEM Unlock" is on
While you’re at it, also enable VoLTE (this must be done in stock rom)
Go to the dialer app and use the IMEI code to identify your IMEI number

On your desktop, put your IMEI number into the site to receive the unlock code. Keep that code around for the next step.

Not a bad idea to save off your IMEI number and the unlock code. I don’t expect that it’s needed after you’ve unlocked, but worth keeping around.

Flashing

This guide mostly works. Summarized here.

First make sure you have latest platform-tools. This is actually important, because at time of writing the fastboot from package managers on Mint was at a version too low to achieve everything.

Boot into bootloader by holding down vol dn and connecting the USB cable.
Once the LED is solid blue:
```
fastboot reboot fastboot
```
It will boot to the fastboot menu.
If this is your first time flashing, then do the following; otherwise skip this step and continue.
```
fastboot oem unlock 0x<code>
```
Highly recommended at this time to flash fastbootd, do so with
```
fastboot flash boot boot_lineagerec.img
```
Reboot the phone into bootloader with the menu option.
- That should bring you to a different, but similar, fastbootd menu with recovery. The reason this is necessary is to avoid the stock bootloader’s refusal to sideload gapps due to signature verification.

Now comes the part where you flash the various partitions, in order. From the images/ folder…

fastboot flash boot boot.img
fastboot --disable-verity --disable-verification flash vbmeta vbmeta.img
fastboot --disable-verity --disable-verification flash vbmeta_system vbmeta_system.img
fastboot erase metadata
fastboot flash system system.img
fastboot flash system_ext system_ext.img
fastboot flash product product.img
fastboot flash vendor vendor.img

Also, if you’re doing this from stock like i was, you’ll also want to do;
```
fastboot erase userdata
```

GApps

But before you reboot, you’ll need gapps. I wasn’t willing to go through all the extra steps to get microG to work, so instead I opted for a more standard approach to gapps. However, Opengapps (which i typically use) only has up to Android 11, so use nikgapps for Android 12. I chose Core.

Then, in fastbootd, go to the option to sideload from ADB, then from your machine do

adb sideload ./<nikgapps file path>

Now, reboot from the fastbootd menu and unplug from the PC, you’re all set.

The first boot after a flash is slow, so slow that I thought it must have been frozen on the Lineage loading screen (the arc with a ball). Just give it a full 5-10min to set itself up, it’ll work. From there, the phone’s all yours.