Navigation map update over USB worked (probably)

Reading on the forum about possibility to upgrade navigation maps using USB stick (somebody mentioned that cars in Russia without data package on the eSIM are using USB to update maps) I decided to try this procedure.

My initial driver was that a large roundabout near me was reconstructed (a year ago) with a tunnel underneath and maps that came with the car showed old information that was used during roundabout reconstruction.

First, I tried the online update. After I installed Skoda connect app, registered and declared my user as primary, infotainment updated navigational database from 20.3 to 21.3. But unfortunately that didn't solve my problem with the map, my roundabout stayed the same with old roads around him. After driving couple of days irritated how can a year old change still not be updated in the current navigation data, I tried the USB procedure:

1. From the https://updateportal.skoda-auto.com/ I downloaded 25GB of ECE 2020/2021 maps
2. As I didn't have 32GB USB stick I used old 2.5" HDD in external enclosure with USB-C cable. This proved very useful because this enclosure has activity LED so you can see if something is happening with the disk
3. I used MiniTool Partition wizard under windows to format my 80GB HDD with FAT32 4k cluster size as per instruction on update portal
4. I extracted the zip file on the the drive
5. I started the ignition, waited for infotainment to boot and plugged the USB disk to the socket closer to the gear selector
6. The LED on the HDD started blinking, you can defensively see when disk is mounted and than infotainment started reading and copying data from the disk. This lasted about 10-20min. It is hard to say exactly how long because i was mounting fire extinguisher under the driver seat. When LED stop blinking I unplugged the disk.

After the procedure was done I powered down the infotainment by long pressing the power button. After the infotainment booted again I immediately checked the navigation databases version and to my surprise it showed the exact same number 21.3. Disappointed, I turned of the car and went home.

The next morning on my way to work I noticed that roads around my roundabout were showing correctly with the new tunnel underneath. Now the navigation didn't go mad when I went through the tunnel. After arriving to work I checked the navigation database and it still showed the same old version number 21.3. Now I was confused. The maps definitely changed but the version under System Information remained the same.

It remains mystery what information is pushed over the OTA update and what information was copied from the USB disk.

If somebody also has  some know road that is missing on the map you can try this procedure and check if this helps.