Doesn't the latter imply the former?
If it's possible to find an LLM for any given problem, then find an LLM for the problem "find an LLM for the problem and then evaluate it" and then evaluate it, and then you have an LLM that can solve any problem.
It's the "Universal Turing Machine" for LLMs.
I wonder what's the LLM equivalent of the halting problem?