Is there a way I can get a diff of the docs every time a new Unity version is released? Unity has actually put considerable effort into making the docs for established systems better over the last year, and there are many cases where knowledge that I've had to work out by prodding the system could be confirmed. A great example is MeshFilter.mesh, which for years had some very terse documentation (something like "returns the mesh used by the meshFilter") but now includes much more code-level explanation. It would be great to have a way, on a new release of the docs to know "ooh, a load of changes were made to the foo subsystem docs, I should re-read them."
You really can't. But, I would at least think there are documentations available for LTS versions, if significant documentation changes were added/removed from the previous revision. I mean, you really don't want to have new documentations no longer mentioning previously known information in LTS version 1, but it was removed in LTS version 2. (For example, of course.)