Linux



Linux (or GNU/Linux if you're nitpicky - and be sure to pronounce it correctly) is a family of free Unix-like operating systems.

Even though its desktop presence is still modest, Linux is immensely popular in pretty much every other field: smartphones and tablets (as Android is derived from it), embedded devices, internet servers, scientific supercomputers, corporate mainframes, graphics renderfarms, and so on. Now that Windows 10 is quite literally spyware, and Apple's machines are as overpriced as ever, you are well advised to look into this.

Now you may ask: "Sure /tech/ies love this thing, but what about the vidya? And is it usable by non-super-nerds?" True, Linux has far fewer games than Windows. But these days, all major engines are designed with multiplatform in mind, so ports have become easy and cheap to do, and digital distribution helps reduce costs. Also, Linux is not really harder to use than Windows, although the sheer amount of options can be intimidating. For instance, the first thing you must do is choose one out of hundreds of distros, and then you can still customize it to a great extent.

Other than native games, there is Wine, a compatibility layer to run Windows applications (there are frontends to make it easier to use). Also, Valve has started a project called "Proton" that delivers Windows games to Linux machines already embedded on a customized Wine wrapper, and it appears to you like if it was any native game on Steam. It is not perfect, but over a thousand games were reported to run very well. Check the compatibility list.

Free games from repositories
To download and install programs on Linux, one typically does not download executable files from various websites and run them by hand; instead, distros provide a software repository or package manager. If something is not in your distro's manager, you can still port the package over but you might need to puzzle out some missing dependencies. For those of us who love to tinker on the engine more than driving the car, you can get the source code for each of these and compile it by hand.

Free games in distro-agnostic packages
These are still typically free software (or at least freeware), but do not use your easy-peasy package manager to install itself deep in your system. Most of the time, they are just binaries (or executables in Windows parlance) in downloadable tar.gz archives (which work like .zip files). Though, in some more rare cases, these may also include games that come as source code only -- you need to hunt down the right libraries through your distro's package manager, compile, and install manually (while trickier, this has the added bonus of increased optimization for your computer hardware, however marginal).