https://www.gamespot.com/articles/how-to-play-play-ghost-recon-wildlands-for-free-th/1100-6461859/

Looking for something to play this weekend and don't want to spend any money? Ubisoft's open-world action game Ghost Recon: Wildlands will be free this weekend on PS4, Xbox One, and PC, but only for a limited time.

From September 20-23, Ubisoft will offer the full game, as well as some of its PvP and PvE missions, to everyone on all platforms for free. Presumably the progress you make during the free weekend will carry forward to the full game should you decide to pick it up.