For us it is relatively straightforward. Every release gets one single post. It always gets a title highlighting the most important change highlighting why people want to upgrade. This is followed by a short summary of which usecase is now supported by a change we did (either added feature or some enhancement). This is again followed by a detailed story on the items above and finally a granular list of security, interface changes, etc., pointing at the relevant ticket number containing for each change the full reasoning and history.

Mostly this is a manual effort on the textual bit. A PR is required to indicate whether something is worthy to be specifically mentioned in the release notes. The list of concrete changes is automated.