Not a whole lot, the entire game is 468 MB and uses around 600-800 MB when running.
The game can run using opengl but it isn't really supported as the game relies on a bunch of the newer vulkan and dx12 features for some of the shaders. In opengl mode there are a lot of graphical issues but the game should be fully playable.
You can launch the game in opengl mode from the command line / terminal with the "--rendering-device opengl3" flag:
HardStuck.exe --rendering-flag opengl3