Thanks for your reply @mrt10001
I have unlocked the bootloader with a code provided by Sony. This may sound dumb but where do I find a stock Android 8.0 rom for this device?
I have Sony's flash tool and will use that however a bit stumped with the rom.

It's been a few years since I've done anything vaugley technical with an android device and remember next to nothing

Hi there,

Recently I purchased a second hand F5121 for the purposes of installing Ubuntu Touch. The one I have received is running Android version 7.1.1. I Note that the device page on the Ubuntu Touch website says I need a minimum of version 8

"Ensure you have upgraded the stock firmware at least to Android 8, else you can't flash the OEM binaries for AOSP. It is best to ensure that you have all the latest firmware installed."

I know this device /can/ get Oreo however whenever I check for updates on mine it says the device is completely up to date
I suspect this may be due to the device being out of support. Does anyone have any advice or guidance? It would be very appreciated

Cheers
Dr. Kebab