GLFW doesn’t seem to be able to detect the steam controller via glfwJoystickPresent yet, is there going to be support for them in the future?
If possible, yes. Any game going up on Steam should use Valve’s API for it, however.
The Steam controller is not exposed via the normal APIs unless you are running via Steam. If you’re releasing for Steam, use Valve’s controller API instead of the GLFW API to fully support all its features. Otherwise there isn’t much to be done, as far as I know.