Preheat oven to 450 degrees. Place potatoes on a rimmed baking sheet and rub with 1 tablespoon oil. Bake until easily pierced with the tip of a paring knife, 45 minutes to 1 hour.
Meanwhile, in a large skillet, heat remaining oil over medium-high. Add garlic; cook until golden, 1 to 2 minutes. Using a slotted spoon, transfer garlic to a paper towel to drain.
Add as much kale as will fit in the skillet; season with salt and pepper. Continue to add kale as the leaves cook down. Cook, tossing frequently until tender, 3 to 5 minutes. Stir in vinegar and red-pepper flakes.
Open each potato; add salt and pepper. Top with ricotta, kale, and garlic.