¡Hola Fg109, Richard-Sel1 y Steven-W15!
This can be quite a tricky question! The answer is that whether you would use ser or estar to talk about food depends on the circumstances.
When talking about food, you use ser to describe specific dishes, because these are general statements that are not temporary (e.g. Quesadillas son deliciosas "Quesadillas are delicious"). You also use ser if you're talking about the food at a particular restaurant or venue, because this is also not temporary (e.g. La comida aquí es muy buena "The food here is very good").
If you're talking about the taste of a particular dish (like one that you just ate), however, then you use estar, because you're talking about a specific bit of food or dish that is not permanent.
(Thrown into this mix is also colloquial regionalisms, of course - you might find that people in one particular region will prefer to use ser or estar in certain situations. Or people might use one or the other to give a particular nuance to their sentence.)
So in the Travelogues lesson where La comida estuvo deliciosa también is said, Miguel is talking about the taste of food that they've eaten - this is why he uses estar.
In Lesson 9.4, the question ¿Y cómo fue la comida? comes after the question ¿A cuál restaurante fuiste? "Which restaurant did (you) go to?" Therefore, in this context, our question could be a shorter form of ¿Y cómo fue la comida en este restaurante? which is why ser is used. It's true that this isn't immediately obvious from the lesson, however - I will forward this to our development team and see if we can make this clearer in the lesson.
I hope that this was still helpful!