My hobby project — npmcharts, is a single-page app that shows the download trends of various npm packages. If you went looking into which headless chrome library to use, you’ll see this graph in your browser. However, when that page is shared to Facebook, Twitter or Slack, the preview image that shows up would all be the same — the screenshot I took comparing frontend frameworks and uploaded as the site’s sole Open Graph image two years ago. Tsk tsk.
Here's an article on how to run a personal screenshot service on a $5-per-month VPS