If you need to dig this hard to find something interesting with a probability of 1, that's pretty good evidence that the vast majority of interesting statements are not of the true/false variety.
Although I don't find it interesting, I am open-minded enough to ... embrace.. the .. uh.. diversity of the world, that allows some people, to find that interesting.
The language that contains all Turing Machines that halt on all inputs is not decidable.
Or
e^(iy) = sin(y) + i * cos(y)
Are those uninteresting trivialities to you?
And these things are exactly the sort of thing that "differ from [trivialities about triangles] only in degree of complexity".
Note that "all triangles have 3 sides" is probably an axiom, but "all triangles have less than 11 sides" is a trivial theorem.