Unlike newer "Discover Media" systems, the RNS 315 requires an SD card with a specific that matches the encrypted data.
Once you have a compatible Eastern Europe SD card, follow these steps:
V12 (2020-2021) is widely considered the final official major update for this hardware.
This update is compatible with the following systems factory-installed in Volkswagen, Škoda, and SEAT models (approx. 2010–2015): RNS 315 (Passat, Golf, Tiguan, Jetta, etc.) Škoda: Amundsen+ SEAT: Media System 2.1 or 2.2 Updating RNS315 maps for fun and profit - danman's blog