After analyzing every method—official and unofficial—here is the final recommendation for different user profiles:
They mimic a local Steam network ID to authorize the game client. dota 2 non steam
Launching via a modified executable bypasses the Steam login prompt. dota 2 non steam
The 5-10GB saved by using a non Steam crack is not worth losing thousands of hours of progress. dota 2 non steam
Understanding Dota 2 Outside the Steam Ecosystem: Methods, Risks, and Alternatives