Instead of using internal temperature to judge when a sourdough porridge bread is properly baked, focus on the crust color. The darker the better.
During the bake, the crust color changes from golden to tan and then to brown. The first time you bake one, a sourdough porridge bread may look done when its crust is evenly brown. It’s not done, the interior is very moist. Keep baking.
The next color stage is a deep brown. A few charred spots is a good sign. Continue baking and you’ll see a reddish glow to the crust. Aim for this deep brown color with rich red tones.