I suspect each platform does its own thing with respect to dictionaries. I haven't heard of any that link dictionaries on a per book basis, but that does not mean that none does. I suspect most rely on book language metadata. I do know that kindle lets you switch among dictionaries in a menu.
There is a sticky dictionary thread in the kindle forum that is kindle centric but not exclusively kindle in content.
https://www.mobileread.com/forums/sh...d.php?t=131137
I got interested in this topic when I was reading an over 100 year old book with much of the spelling quite different from today. I got very frustrated when I could not look up the many words I wasn't familiar with and decided to make my own dictionary. In the early days of struggling with this, I came up with the glossary in front idea, which worked well and was easy. I never finished the glossary, but if I ever go back, that is what I would do. Unless, of course, someone ever presents a way to construct a dictionary that would be easy for me to follow. What I find easy or difficult might not match the experience of others.