I found them. It seems they're not included with the post about the firmware, but if you do a search for "Unity hub", this will present a list of search results where the "Dell Unity Info Hub: Product documents and information" holds the information I was looking for. The point is that I didn't know I had to search for this in the first place. I searched for "Release Notes" and didn't find anything.
Whenever a new firmware of for example a Unity is published, they always refer to the release notes, but where are these RN? Wouldn't it be a good idea to name AND link them in the text about the firmware itself? I'm trying to find the RN of Unity f/w version Unity-5.1.3.0.5.003, which came out 2 days ago, but after half an hour of searching I have to give up. I just cannot find them.
Where can I find Release Notes (of Unity firmwares)