[Galaxy Note Pro 12.2 Q&A, Help & Troubleshooting] tizFaver:
Hi, in this guide I will help you to root, install the TWRP, and install LineageOS 17.1 (or any custom ROM for this tablet).

I'm not responsible for any damage to your device of any sort.

By flashing this you take responsibility of anything that happens.

Process at your own risk!

This firmware was developed for the p905. It doesn't apply to the p905v at this time because it's bootloader locked and a custom recovery isn't possible.

Doing this you will delete all you file, so before starting save you important data in a different device.

DOWNLOADING​

Download this .zip that have all the required files: https://drive.google.com/file/d/1aXfW2WoNER0kKRUc6dn0Odu3VW2swNA7/view?usp=share_link

Extract the folder in the Desktop for better agility.

STARTING​

Open the folder previously extracted, and run as administrator the .exe "Samsung-Usb-Driver-v1.5.59.0". Now you downloaded the Samsung drivers.

Now run as administrator the .exe "adb-setup-1.4.3 run as admin": Answer yes for every step asked.

Remember to install the GAPPS from here (i didn't put them in the .zip file because uses al lot of space): https://opengapps.org/ (select the ARM and Android version, that in this case is Android 10.0, and I choosed the nano version, but you can select which you want in base of included app: https://gapps4android.wordpress.com/2016/03/20/gapps-package-comparison-which-to-choose/ ).

Store the .zip with the gapps in the tablet, in some location that you will remember.

In the extracted folder you will find the rom .zip file of the LineageOS 17.1, do the same as for the GAPPS .zip, so copy it in the tablet in a folder that you will remember.

This process will NOT require the OEM unlock, because Odin will do it for you.

Be sure to have enabled the USB debug in the Developer Options. Plug the tablet in the PC and be sure that the tablet ask you to enable USB DEBUG via your PC. Is no pop-up is asking you this, open the folder extracted, go to "fastboot" and open a CMD in this location, and type the command: "adb devices" this will trigger the tablet to ask you to allow the USB debugging via your PC.

ROOTING​

Put the Samsung Galaxy Note pro 12.2 in the Downloading mode:

1. turn off the device completely.

2. hold down the POWER key and the volume DOWN key.

3. when you come out a screen with a yellow triangle and an exclamation mark and asking if you want to be sure to enter the Downloading mode (also called Odin Mode), to agree click the volume UP button.

Meanwhile start Odin (the file .exe called "Odin3-v3.10.6" that is in the extracted folder) as administrator.

Now plug the Galaxy Note pro in the PC and you will se now a message in the left box saying something like: "<ID:0/005> Added!!" the number is based on the COM port that your tablet is now connected (in my case was 5).

Now click on the button "AP" (that should be the only one clickable) and select the file "CF-Auto-Root-viennalte-viennaltexx-smp905.tar" in the main extracted folder.

Finally now click START. In my case took 5 minutes to complete.

When the process ends, the tablet will reboot automatically, and in the apps you will see an app called "superSU". If you see this app, you successfully rooted you device!

Open the new app and it will ask you if you disable Xnox and you will click yes, or ok.
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INSTALLING TWRP​

We will install TWRP in the Easy way, from the Play Store. So open the Play Store and download the officiall TWRP app.

Once downloaded, open the app. If the app ask for request from superSU you will need to GRANT.

Ok, now click on the "Select Device" and choose our tablet, the Galaxy Note Pro 12.2, and choose the latest .img avaible. It will ask you to download, so you click OK and it will open the browser and download the image file (should be called like "twrp-3.0.2-0-viennatlexx.img"). Remember where it got downloaded and return in the TWRP app. Now click on "Select a file to flash.." and select the image file now downloaded. Finally click on "FLASH TO RECOVERY" and in the pop-up click OKAY.

You should get a screen saying "Flash completed successfully!".
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INSTALLING LINEAGEOS (or any rom)​

Boot in the TWRP mode by connecting the device to the PC, opening the folder "fastboot" in the firstly .zip downloaded and opening the cmd in that location. Once you opened the cmd, type "adb devices" and now you should see you device. Now type the command: "adb reboot recovery". Your device will shutdown and automatically restart in the TWRP mode.

From here you can follow any Tutorial in the web to install the rom and the gapps.

But if you want to install now the rom LineageOS 17.1, continue following this guide.

Once you are in the TWRP mode, click "Wipe" and go to "Advanced Wipe" and select only the checkboxes "Davlik Cache", "System", "data" and "Cache". Now swipe to wipe.

Now go back in the main page, and click "Install" and navigate where you have the ROM .zip file stored of the LineageOS rom. When you find it click on it and Swipe to confirm Flash.

Now DO NOT reboot the system, go back and Flash in the same manner the .zip file with the GAPPS. After flashing the GAPPS, remember to click on the button "Wipe cache/dalvik".

NOW FINALLY CLICK ON THE BUTTON REBOOT SYSTEM. And here you go, that's how I upgraded from Android 5.0.2 to Android 10 for my tablet Samsung Galaxy Note Pro 12.2 SM-P905.
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CONCLUSION​

I only wanted to share my experience, because I had really hard time trying the upgrading becuase internet was not really clear about this.

If you have any problem I will try help you in this Thread, but i'm not an expert, i'm only a guy that searched the web alone.

Buona fortuna a tutti e Arrivederci!​