I am posting here because Pro is what started my desire to find this.
Where can a person get, hopefully in one place, a comprehensive list of changes to software. For example, I had been forgetting to update my Pro software and did it just recently, however, now only then did I discover that I must upgrade License Manager to continue to licensing Pro through Portal. Why a minor version change requires changing a existing, supported, server stack is an aside with strong opinions; but where could I find this information? I found it on the software requirements page for Pro 2.9 but nothing in the release's blog post, which seems mostly focused around marketing.
Is there a secret sys admin page where I can just a list, hopefully less pictures and more text, of changes from version to version? The ArcGIS Pro 2.9 Issues Addressed seems to only address bug fixes and I could not find any notice of the License Manager requirement. The Release Notes page for ArcGIS Pro 2.9 doesn't seem to address this either.