Anyone who has amazon prime should check out the "prime gaming" page tor free GOG keys. There are loads of games from like Scorn to Baldurs Gate; Call of Juarez to Dredge. All totally free to keep on GOG from the keys Amazon give you.
They are a shitty company but this benefit is not well publicised enough and probably won't last forever so worth taking advantage. There are Epic cd keys on there too but I don't use it personally.
Edit: Last bit of testimony - it has cured me of my humblebundle addiction where I picked up the low tier every month. Growing my GOG library has been satisfying so I have at least some kind of backup from Steam (just in case the unthinkable happens).