Several specific contexts exist where the article is expected in Greek, and not in English. It's normal to need the article in Greek (It is probably not helpful to most users, but ... if you can use Portuguese as a guide, it seems pretty close to Greek in this usage.) When translating Greek to English, if the article is there and it sounds OK in English to, keep it.
Only old (?) beef -"βοδινό" and pork -"χοιρινό". Younger beef (but not feeding with milk any more) is "μοσχαρίσιο", lamb meat is "αρνίσιο", kid goat meat is "κατσικίσιο" and for the other meats we don't have have adjectives, we just use the name of the animal (chicken - κοτόπουλο, veal - μοσχαράκι γάλακτος, sheep (mutton) - προβατίνα, goat - γίδα, rabbit - λαγός, κουνέλι, duck - πάπια, wild boar - αγριογούρουνο etc).
The "-ινό" (and "-ινο") is generally one of the suffixes in adjectives used to describe from what is made the following noun (the suffix "-ίσιο" is another one). For example, the forementioned meats, αγελαδινό γάλα is cow's milk, χάρτινο καράβι is paper boat (origami), μάλλινο πουκάμισο is woolen shirt, πήλινο βάζο is clay vase etc.
In Greek, is the definite article used in general statements? Duolingo does not seem consistent about this. I translated this phrase as "Pork and salad", taking it generally, and this was marked wrong. So does this phrase with the definite articles have to mean "The specific piece of pork and the particular salad" that we are looking at? In another DL question I have translated "Meat" (not "The meat") as το κρέας with the definite article, meaning it generally, and been marked right. Please can you clarify?
Thank you. Just so I understand, would the correct Greek translation of "Pork and salad are popular around here" be "Το χοιρινό και η σαλάτα είναι δημοφιλείς σ´αυτό το χώρο" or "Χοιρινό και σαλάτα είναι δημοφιλείς σ´αυτό το χώρο"? Or doesn't it matter? Are they both all right?
The former, because the definite article in Greek is virtually always mandatory when the respective noun is the subject of the sentence.
Some corrections: It's "δημοφιλ-ή" (3rd declension adjective) because the word implied is either "πιάτα" or "φαγητά", which are both neuter.
"Σ' αυτόν τον χώρο" means something closer to "in this room". Instead you can use "Σ' αυτό το μέρος" (place) or "εδώ πέρα" (literally, " here over") or "εδώ γύρω" (literally, "here around").