Cyan Gimp Plugin -

Install it, run it on a high-contrast black-and-white image, and then add a subtle noise layer (Filters > Noise > HSV Noise) and a paper texture. The result will rival paid plugins.

Disclosure: This review is based on the commonly available Cyan plugin (version 1.2) as found in Ubuntu’s repos and various GIMP plugin collections. No affiliation with the developer. cyan gimp plugin