What is your advice to someone who frequently brings up the topic of polygyny with his wife in a country where polygyny is prohibited?

There is no disagreement regarding the permissibility of polygyny if the man is capable of bearing the financial burdens of marriage and maintaining justice among his wives. Any law that prohibits this is unjust and contrary to Islamic law. It is not a condition to inform the first wife of a second marriage. If he does inform her, there is no need for excessive discussion on this matter, especially if he does not intend to marry another, as this could provoke jealousy and anger, which contradicts good companionship.