Bring 4 quarts water to a boil over high heat and add 2 tablespoons salt.
Add farro, reduce heat to a brisk simmer, and cook until al dente, stirring occasionally. Cook time is ~20 minutes soaked, 30 minutes unsoaked.
Drain farro and spread out on a small rimmed baking sheet or platter to cool. Meanwhile, in a large bowl, combine scallions, chile, and vinegar and season with a 4-finger pinch of salt.
Stir to combine and let sit 10 minutes for flavors to meld.
Add farro to bowl with the scallion mixture, along with anchovies, cucumber, and olives. Toss to coat, then add olive oil and feta and gently fold together.
Taste and season with salt and pepper. Just before serving, add romaine and mint and toss gently to combine.
Recipe Note
Note: The recipe time does not account for overnight soaking, but if you're using pearled or semi-pearled farro, you don't need to soak it.