darktable (and some other projects, like for example ufraw) don’t do any real lens detection or correction by itself. We depend on two libraries which in most cases are provided by the Linux distribution you’re using.
Lens Detection Many image files contain metadata about how the image was created. In case of digital camera images, a standard called Exif is used, this standard allows a camera to record many details about how an image was taken.
This is a companion discussion topic for the original entry at https://www.darktable.org/2015/02/on-lens-detection-and-correction/