Numberphile published an hour long video [1] about the Langland program, which dives a bit into this "grand unified theory of mathematics". I'm not a mathematician, but I find these topics fascinating.
> I’ve never succeeded in understanding the slightest thing about it.
[0] https://golem.ph.utexas.edu/category/2010/08/what_is_the_lan...
(Category Theory, of all things, being the best tool for formalizing dualities and all sorts of analogies between seemingly different objects of study.)