The game is free on Fanatical, although for a limited time, if you’re willing to jump through a few hoops. To claim it, you need to (1) create an account; (2) connect your Steam;* (3) verify your email address; and (4) sign up for their newsletter.

‎* Your Steam account must not be limited in that you have to have spent at least five US dollars within the Steam store.

Update
Congratulations to rookierose!