You can find the downloads here:
https://mega.nz/folder/b4VkmDJJ#PE2C7Te_Yl0pw1TydB--Bg/folder/alt21SoQ
For your car the latest download is: "MST2_EU_SE_ZR_P0479T.7z"
I have flashed that exact same firmware on my car successfully a couple of months ago, and did not have any issues so far.
If I remember correctly, the flashing procedure is this:
You need an SD card of 8 GB (or more). Make sure the card is formatted as FAT32 before you copy anything to it.
Extract the contents of the archive (mentioned above) into the root folder of the SD card.
Go into the car, and make sure you take out the navigation SD card if you have it in your storage drawer / glove box compartment.
Put the firmware SD card into slot #1. Again make sure slot #2 is empty.
Start the car or put the battery charger on your cars battery.
Press and hold the "Menu" icon (located below the car icon in the right column of icons) on the head unit until a hidden menu appears.
Once inside the menu you should see an option to update/upgrade firmware. Follow its instructions.
The process takes about 15 minutes to complete, depending on how fast your SD card is.
*And lastly, if I remember correctly* Once finished, you will get a question if you want to cancel / rollback the update. Say no...
It will than say an error occured, but that is normal. Press ok / continue, and you are finished.
You can shutdown/restart the head unit, by holding the power button, and check that you now have the version "479".
To explain why the error occurs at the end of the flashing process:
It is used internally for Seat / VW to see that there was a change in the software version of the head unit.
The exact error description is "Confirmation of version change". So that if a customer complaints their head unit does not work, they will see that it was tampered with unofficially. This error can be removed using OBDEleven or VCDS, but it does not have any negative impacts on the head unit.
My car has the error still active since I don't own VCDS or OBDEleven.