You can still buy used physical discs for Xbox One, which are playable on PC via "Xbox Play Anywhere" if you have a digital license.
Forza Horizon 3 was officially from the Microsoft Store and digital retailers on September 27, 2020. This means the game is no longer available for direct digital purchase or download for new players. ⚠️ Current Availability Official Digital Purchase: No longer possible. download-forza-horizon-3-game-for-pc-full-version
If you are looking for the Forza experience on PC today, these titles are actively supported and available: The current flagship set in Mexico. You can still buy used physical discs for
Searching for "full version free downloads" for delisted games often leads to: If you already bought it, you can still
Set in Britain; still available for purchase and widely praised.
If you already bought it, you can still download and play it from your "Owned" library.