[Xperia Z3 Tablet Compact Original Android Developm] CricriTheLord:
Here a step by step procedure I wrote, based on my own experience

Update Android to 11 on Xperia Tablet Z3 Compact (SGP611)

I. Prepare your computer and the device to interact

1. Download and install xperia adb drivers (https://developer.sony.com/file/download/xperia-z3-tablet-compact-driver/)

2. Download and install adb platform-tools (https://developer.android.com/studio/releases/platform-tools?hl=fr#downloads)

3. Activate debugger on the device

a) start android and go to settings

b) in the version build number info tap multiple times (7 would be ok, more is not a problem) to enable developer options

c) go to the developer option (should appear close to the about section in the settings)

d) enable USB debugging

II. Unlock the bootloader

1. Check bootloader lock : https://developer.sony.com/develop/open-devices/get-started/unlock-bootloader/

a) Open the Contacts app.

b) Click the menu button in the top right.

c) Click Settings.

d) Long press (for about 5 seconds) somewhere in the empty space just above soft key bar, and then release yoeur finger. A button named Enter service code will then appear in the same area (this may take a few tries).

f) Click Enter service code. A dialer will appear.

g) Enter *#*#7378423#*#* in the dialer.

h) Tap Service info > Configuration > Rooting Status. If Bootloader unlock allowed says Yes, then you can continue with the next step. If it says No, or if the status is missing, your device cannot be unlocked.

i) [My addition] If status says unlocked: Yes, the device is already unlocked, you can pass the next step

2. If not unlocked, unlock the device following the steps on sony.com website

III. Enable recovery mode

!! The default bootloader doesn't allow recovery mode to be activated, I couldn't find any other kernel to enable it, so I finally decided to get it from Cyanogen, and it worked, but the lineageos zip contains a boot.ini file, maybe you can use it

1. Get the kernel image from Cyanogen 12.1 zip package (boot.img in the file cm-12.1-20161016-NIGHTLY-scorpion_windy.zip) and copy it in the platform-tools folder

Could be:

1. Get the kernel image from the lineageos zip and copy it in the platform-tools folder

2. Flash the kernel on the device :

a) Turn the device off and wait 5 sec.

b) Start a command line in the platform-tools folder

c) Start the device in fastboot mode (when turned off, keep pressing the volue up button while pluging the usb cable, keep the finger on volume up button while the led indicator turns in blue

d) check fastmode mode, in the command line, run : fastboot devices

e) your device should appear, if not restart fastboot mode on the device

f) flash the kernel : fastboot flash boot boot.img

g) restart the device : fastboot reboot

Now, the device is able to start the Cyanogen recovery (by pressing volume down button during boot sequence)

3. get the pbrp recovery image and copy it into the platform-tools folder

(https://drive.google.com/file/d/1VOnGXn7esVwz1nSTuuuSRHFvR1FX6H_t/view?usp=sharing)

4. replace the Cyanogen recovery (Lineageos package won't run in it) -- If you installed it, if not, you can bypass this step

a) Turn the device off and wait 5 sec.

b) Start a command line in the platform-tools folder

c) Start the device in fastboot mode (when turned off, keep pressing the volue up button while pluging the usb cable, keep the finger on volume up button while the led indicator turns in blue

d) check fastmode mode, in the command line, run : fastboot devices

e) your device should appear, if not restart fastboot mode on the device

f) flash the kernel : fastboot flash recovery pbrp_9.0_z3tcw.img

g) restart the device : fastboot reboot

IV. Install Lineageos package with google apps (https://drive.google.com/drive/folders/1xzpvnZ-PVlKVw3rgALEzMxcpqPkxPNIT?usp=sharing and https://androidfilehost.com/?fid=17825722713688288530)

1. Start the device in recovery mode

a) Turn off and wait for 5 sec.

b) turn on the device, wait for Sony logo to appear

c) while the boot Sony logo is displayed, press multiple times the volume dosn button, until the led turn in blue

d) the device should be started in recovery mode

2. Copy packages in the device' sdcard

a) plug the usb cable to the device and the computer, recovery should enable MTP transfers

b) On the computer, copy both packages (lineage-18.1-20230318-UNOFFICIAL-z3tcw.zip and MindTheGapps-11.0.0-arm-20220217_095902.zip) on the device, with explorer

c) it should take few time

3. Flash the packages

a) In the recovery program, select the Install option

b) change the files view to sdcard

c) select the file lineage-18.1-20230318-UNOFFICIAL-z3tcw.zip

d) click on Add new package

e) select the file MindTheGapps-11.0.0-arm-20220217_095902.zip

f) use the slider to validate the list and flash, it will take some times

g) select reboot to restart the device

Your Xperia Tablet Z3 Compact now runs android 11 with google services enabled.