Do you process data of your users or readers for whatever purpose (to stay in touch, to share important updates, to see who is visiting your website etc.)? If so, then the GDPR applies to you. It applies to all sorts of data processing, regardless of whether it is done for profit or on non-profit basis, with few exceptions.
Individuals are exempt if they collect data for ‘personal or domestic use’ – for example if they store personal contact details on their phone. But this exception does not cover blogging if it is public and professional (not personal) activity.