One feature of G2A that seems pretty dodgy is that they make you pay extra for "G2A Shield", in which case they actually insure your purchase against fraud. There was one time Ubisoft identified a large number of black market keys and revoked them, but then all the users who bought those keys through G2A complained and Ubisoft caved in, saying they could keep their copies of the game. Ubisoft didn't want to be the bad guy, but that only helped the black market. If you buy a black market key, don't blame Ubisoft or Steam if it later gets revoked.
Both G2A and retailers both need to clamp down hard on illegal activity so that it is not profitable. Retailers need to revoke these keys and G2A needs to take full responsibility every single time for any black market they're facilitating.
At best, G2A is a grey market. Even when the keys are 100% legit, publishers and retailers dislike it. But they also hate it when a console gamer resells their physical disc (unless they're the retailer reselling it). PC gaming is one of the few industries to have successfully destroyed the second-hand market. I'm not going to argue it's the end of the world.
At this stage, it doesn't appear that there's any way to obtain a D:OS2 key except legitimately via the Kickstarter (any fraud should have been detected by now), so any keys for sale would have to be from this.
But if you're interested in supporting Larian, grey market sales don't help them. The best way to support them is to contribute to a Kickstarter directly or purchase a copy directly from an official retailer like Steam or GOG. I expect it will be sold at a similar price on Steam in a few days anyway.
