Having a great time with 'Cthulhu Realms' card game on steam, its free but has a dlc for £4 but that's all you pay.
its on steam and on iOS I will be buying on iOS aswell its so much fun
It's Star Realms with a Lovecraft theme. Which is fine for a light-ish deck builder card game.
Ascension is another deck builder to PC port, but it has a lot more cards in it from all the expansions.
Not sure if there are any other digital deck builder ports out there.
I love the theme, its got atmosphere, I saw star realms but didn't grab me like this one.