Players who own the game on older consoles (PS4/Xbox One) can download the Gen 9 update for PS5 and Xbox Series X|S at no extra cost.
Sandstorm: “Operation: Overrun,” New Major Update Now Available operation-sandstorm-pc-game-free-download-full-version
The developers occasionally host "Free Weekends" where the full game can be downloaded and played for free for a limited time. Players who own the game on older consoles
It is important to distinguish between free updates and the full game download: operation-sandstorm-pc-game-free-download-full-version