Heat the olive oil and butter in a medium skillet. Stir in the onion and sauté until softened, about 5 minutes. Stir in the rice, thyme and salt, then cook for 1 minute. Add the wine and half the berries. Cook until the wine is almost evaporated. Gradually add ½ cup of chicken broth, stirring until it is fully incorporated. Repeat with the remaining broth, ½ cup at a time, cooking until the rice is al dente, about 30 minutes. Add the Greek yogurt and lemon zest towards the end, stirring vigorously until incorporated and the rice is creamy. Stir in the remaining strawberries and cook for 1 minute. Season to taste with salt and pepper.
Divide the risotto among 4 bowls and sprinkle cheese over each serving. Garnish with fresh berries and more thyme.