Instead of using fat-free evaporated milk, you can also use skim milk or regular milk, although fat-free evaporated milk is the best option as it’s much thicker and creamier, similar to heavy cream.
Spud Lite potatoes or Carisma potatoes have 25% less carbs compared to regular potatoes, but if you don’t have either of those available, you can use russet potatoes, sweet potatoes, etc.