An absolutely lightweight CMS compatible with GitHub Pages and any hosting, including free ones.
Handalf: Unbloated Flat-File CMS
Designed to rank high-quality content, Handalf is a small piece of software that, when combined with a Node.js command, a Python or Bash script, or even PHP, can be updated to read the JSON files in a subfolder and convert them into an index.json file. This allows the other files to be loaded and their metadata read.