Place the spinach on a platter and drizzle with half of the lemon juice, 1 tablespoon of the olive oil, and salt and pepper to taste.
Whisk the remaining lemon juice, remaining 3 tablespoons olive oil, the cider vinegar, lemon thyme, mint, 1/2 teaspoon salt and a few grinds of pepper in a small bowl until combined. Taste and adjust seasoning if needed. Toss the radishes, cucumber, kohlrabi and shallot with the lemon dressing and serve over the spinach. Top with more mint.