The metals which produce hydrogen only with very dilute nitric acid are

Mg+2HNO3​→Mn(NO3​)2​+H2​↑Mn+2HNO3​→Mn(NO3​)2​+H2​↑Metals react with nitric acid, but hydrogen gas is not evolved, because nitric acid is a strong oxidizing agent. So, it oxidizes the hydrogen to water and itself gets reduced to any nitrogen oxide. But, Magnesium and Manganese are two metals that traditionally, liberate H2​ and not H2​O when they react with HNO3.