Mad Max, one of the successful PC games brought to Linux by Feral Interactive, currently has a 50% discount promo at The Feral Store from July 20 – 27, 2018. Feral Interactive earns more money if the game is bought directly from their own digital store. You can buy from them directly if you want to support cross-platform PC gaming and ensure your purchase counts as a Linux game sale. For those who are not familiar with Feral Interactive, they are the game developer who brought to Linux many popular games such as F1 2017, Rise of the Tomb Raider, and Middle-earth: Shadow of Mordor.
You’ll receive a Steam game code when you purchase a game from The Feral Store and Mad Max supports Steam Play which means you only purchase the game once and it can be played on Linux, macOS, and Windows. I have already bought games from The Feral Store a couple of times using my credit card and I did not have any problems with it. They also send through e-mail an official receipt and a copy of the Steam game code for easier tracking of your purchase.