Back when using the MySQL manual this was a little less of an issue, even when not having access to the original DocBook XML sources, as even the HTML generated from these had some structure to it. So back then I had a script that would spider all the release note pages from the MySQL manual, parse the individual note items, and put them into a database by topic.

That way I could run queries like "give me all InnoDB related change items between version a.b.c and x.y.z" or "give me all changes between a.b.c and x.y.z, grouped by topic".

Never managed to get the same from the release notes in the KB as they lack definite structure and are more or less just free text.

In an ideal world we'd have all the release note items in a database as primary source of truth, and would generate actual release notes documents, for individual minor releases, and for differences between any pair of arbitrary release version numbers from there.

My original project is still somewhat available here:

https://github.com/hholzgra/mysql_changelogs

I stopped providing an actual running instance of it quite a while ago once we stopped being an in-place alternative to MySQL and went to a different version number scheme.