Matrix Games. They’re a publisher that specialize in wargames that I frequent to get some of my more-serious milsims from (though availability has improved on Steam). They also run an online store. The above three stores are the only places that I’ve bought video games for a long time. Well…tries to remember actually, I did get a few things on itch.io, and IIRC I bought Starsector directly from the company that makes that.