In any case, the best approach is to direct them to Steam, offer support for purchasing if needed, and advise against third-party links. Emphasize legal compliance and security. Maybe also suggest looking into community resources like the SCS forum or official Steam community for help with mods that require specific ETS 2 versions. If they need to switch between versions frequently for mod testing, there are some guides on how to manage that with multiple Steam library folders or using different installations.