Starting with the best bit: you can get a free game! Genesis Alpha One, a roguelike FPS where you must build, maintain and navigate your ship through a galaxy filled with hostile alien and human threats. If you scroll down on the GOG homepage, you will see the giveaway banner. You have ~72 hours to grab it.
On top of that, GOG will also give you a free copy of The Witcher along with a GWENT Card Keg if you sign up for their newsletter.
They also just released Hands of Necromancy, which oddly doesn't have the Native Linux version on GOG but it does have one on Steam.
Some quick picks:
- State of Mind - 90% off
- Darkest Dungeon - 85% off
- Iratus: Lord of the Dead - 80% off
- Stygian: Reign of the Old Ones - 80% off
- Surviving Mars - 75% off
- Fury Unleashed - 70% off
Head over to GOG.com for all the deals. Their sale lasts until November 3rd, 10 PM UTC.
Plenty of their games have Linux versions, otherwise you can try using the Heroic Launcher to run them with Wine which will work quite nicely for a lot of what they have.
If you do find a good deal be sure to leave a comment.