I couldn't find a way to contact the author, but in case he's reading this or anyone knows his contact information: I'd like to subscribe to your blog, but your RSS feed is currently broken.
If you remove the "blog." subdomain and go to https://pipetogrep.org/ you are greeted by a typical "about me" page. It includes a link back to the blog, as well as a mailto link, and links to GitHub and LinkedIn profiles.