We are having rice is present tense in English and would be said when a group of us are eating rice. We have rice would mean we have some rice for example in the house. As 'we are having' was deemed incorrect am I to assume the french sentance means we have some rice but are not eating it?
Using "having" in the sense of eating or drinking something, the French use a different word: prendre. Literally, it means "to take" but when saying something like "Nous prenons du riz", it means "We are having rice" (in the sense of having it to eat, i.e., we are eating it). Some of the Duo sentences force "prendre" to be "take" in this context. That is good French, but bad English. Tu prends du riz = You are having rice (i.e., to eat). Qu'est-ce que tu prends ? = "What are you having?" or "What will you have?"