Heat the oven to 400 degrees F. Line 2 large rimmed baking sheets with parchment.
Put the eggplant slices in a colander in the sink and sprinkle with 1/8 teaspoon salt; flip slices and sprinkle with another 1/8 teaspoon salt. (This step helps remove the bitterness.) Set aside.
Put the bell peppers in a large bowl and toss with 1 teaspoon oil. Spread out on 1 large rimmed baking sheet.
Rinse the salt off the eggplant and pat dry with a paper towel. Put the eggplant in a bowl and toss with the remaining teaspoon oil. Spread on the other lined baking sheet and bake the peppers and eggplant, flipping halfway through, 20 minutes. (Leave the oven on.)
Meanwhile, spray a 15-by-10-inch (or 13-by-9-inch) rimmed baking sheet with cooking spray and sprinkle with the cornmeal; set aside.
Combine both flours, the oregano, 1/4 teaspoon salt and a few grinds of pepper in a large bowl. Combine the milk and eggs in a small bowl; mix into the flour mixture until well combined. Pour into the prepared baking sheet and even out the dough. Top with the roasted eggplant and bell peppers.
Bake the pizza for 10 minutes. Turn the oven to the broil setting, and top the pizza with the artichokes, red onion, cherry tomatoes and cheese. Broil until the cheese is melted and golden, about 5 minutes. (Watch carefully.)
Top the pizza with the mint leaves and serve with lemon wedges if using.