GOG if available, no DRM and while I think they do have a launcher, I don't think it's required. I could be wrong...
Steam does tend to be annoying about logging in and out, not necessarily letting you choose to update stuff, it has DRM and requires internet (or will at least be annoying about it).
GOG is more like, gosh, downloading some software and then running it. Without it doing 11 kinds of random shit on you.
A movie about a guy and, extremely briefly, his dog.