Product keys for ETS2 generally come in two formats depending on where you purchased the game:
This specific update, also known as the "Holiday Update," introduced several gameplay and technical enhancements: euro truck simulator 2 version 1.15.1.0 product key
If you need version 1.15.1.0 specifically (perhaps for an old mod or a retro PC build), you have two legal options: Product keys for ETS2 generally come in two