Oatmeal Agitante

Halting problem uses a trivial construction of undecidability. My intuition is that "nontrivially undecidable" does not exist

The Arithmetic Hierarchy gives an infinite hierarchy of classes of undecidability harder than halting. Are all 'trivial'?

no, not "trivial". But, "contrived"? Not increasing the risk that I will stumble upon an undecidable problem by chance?

Ahh.

How about these? https://en.m.wikipedia.org/wiki/List_of_undecidable_problems …

I'm not familiar enough with group theory or topology to comment on those. Among the rest, it seems to break down into 2 forms

1. Instantiate the halting problem in X. (trivial) 2. X produces pseudorandom behavior which can't be predicted. (maybe not)

I think I'd be satisfied with 2 if X is of substantial consequence elsewhere in the field