An unofficial Android 7 Nougat ROM is available for download courtesy of folks at xda developers. Before you install this Nougat ROM on your Samsung tablet, you need to ensure you have Android lollipop bootloader as otherwise, your Tab Pro won’t boot. To install it, you will need Tab Pro 12.2 TWRP (link) and ODIN on PC.
1. Make sure you have a full backup because just in case you something fails. Here are the steps to flash this via ODIN. Download ROM from here.
2. Reboot your tablet into download mode. Do this by first switching off the phone, then pressing and holding the volume down + home button together and then pressing the power button. Press volume up button to enter download mode.
3. Open ODIN on your computer. You will see the ID:COM box turning yellow with a COM port number upon successful connection with the tablet.
4. In ODIN click the BL button, select the bootloader firmware. It’s a tar file.
Make sure Auto Reboot & F. Reset Time options are selected in ODIN
5. Click on the start button. When the process is completed your phone will reboot. You can install gapps later via TWRP. Flash this ZIP file in recovery before booting.
Also if you see an error about recovery or kernel, it is safe to ignore it. This error is due to fact you have installed a custom ROM.