Any situation where individuals are pitted against one another is going to be difficult training ground for rationality. Evidence needs to be treated not just as something to deploy against others. Reframing truth-seeking as a cooperative, positive-sum venture rather than an adversarial, zero-sum one can go a long way.

That only holds if the individuals are trying to change each other's mind, or prove that the other is wrong to a third party. If the conflict isn't around belief or values, then the involved parties have better use the available evidence to be as effective as possible. So games like Diplomacy or Starcraft could be decent training grounds for instrumental rationality.

(I still agree with what you meant, i.e. adverserial debate isn't very conductive to either party weighting the evidence honestly and updating their beliefs in consequence)