RH would require completely novel insight and a brilliant original thought. Unlike Navier-Stokes it's not a gradual effort and you cannot piggyback off of other mathematician's works, so "AI" will not solve it anytime soon.

There has been a lot of intermediate progress on the Riemann hypothesis, for example ruling out particular kinds of zeros, and some of those partial results even involve LLMs https://www.anthropic.com/research/riemann-zeta so I don't see why I can't possibly be a gradual effort.