I want to get the Chef Infra Client changelog / release notes of a specific version. This I want in text format. is there any API or any way to get it?
Yes, the docs site repository have a description of how they do it for the pages like Chef Infra Client Release Notes
Each release note page comes from a Markdown file from
https://packages.chef.io/release-notes/<PRODUCT>/<VERSION>.md.
For exemple: https://packages.chef.io/release-notes/chef/17.1.35.md