Place a large mixing bowl and beaters in the freezer for 30 minutes to chill thoroughly.
Add the diced mango and coconut milk to a blender or food processor. Blend until completely smooth, about 1 minute. Set aside.
In the chilled bowl, beat the heavy cream on medium-high speed until stiff peaks form, about 3-4 minutes. The cream should hold its shape when you lift the beaters.
In a separate large bowl, whisk together the sweetened condensed milk, vanilla extract, lime juice, and salt until smooth.
Pour the mango-coconut puree into the condensed milk mixture and stir gently until combined.
Add one-third of the whipped cream to the mango mixture and fold gently using a spatula in figure-eight motions to lighten the base.
Add the remaining whipped cream and continue folding gently until no white streaks remain, being careful not to deflate the mixture.
Pour into a 9x5-inch loaf pan or freezer-safe container. Smooth the top with a spatula and press plastic wrap directly onto the surface.
Freeze for at least 6 hours or overnight until firm. Let sit at room temperature for 5-7 minutes before scooping and serving.
