Hey there, the triumphs are poorly worded. Despite the 'any difficulty' bit, they only pop when playing those missions as part of the weekly rotation of replayable campaign missions, accessed from a node on the Neomuna map, on any of the difficulty options offered there. They will not pop when the missions are played from the campaign mission picker on Normal or Legendary. It was the same for Witch Queen's mission triumphs too, the year before.