Searching for free cracks or "Steam Edition" downloads from unofficial sources carries significant risks:
While the game was still active, there were occasionally free car packs, such as the Mitsubishi Car Pack, though these required owning the base game. Risks of "Free Download" Sites Forza Horizon 4 Free Download (Steam Edition)
If you bought the game before it was delisted, you can still download, reinstall, and play it (both online and offline) as usual. Searching for free cracks or "Steam Edition" downloads
There are only a few very specific ways users might have obtained the game without a direct purchase: there were occasionally free car packs