If you're interested in playing Euro Truck Simulator 2, I recommend purchasing the game through official channels, such as:
The primary source for the most stable version. Humble Bundle: Frequently features SCS Software titles. Product Key For Euro Truck Simulator 2 Version 1.35.1.31
All official product keys for ETS2, whether from the legacy or modern era, now . There is no way to activate a modern version of ETS2 without the Steam client. If you're interested in playing Euro Truck Simulator
A product key is a unique code required to activate and play Euro Truck Simulator 2. The product key for version 1.35.1.31 is essential for users who have purchased the game or are looking to upgrade from an older version. There is no way to activate a modern
According to the official Euro Truck Simulator 2 support page, "all product keys activate on Steam" regardless of which format you have. This means even old physical retail keys can be redeemed through Valve's platform—a decision SCS Software announced back in January 2013 when the game first launched on Steam. As confirmed in an official blog post, "the original ETS2 Product Keys (also known as CD keys) should as of now activate the game".