Translation:The community invites the researcher for lunch.
Nice question! As you already noted, many languages (en,sv, actually probably most slavic and germanic languages) you'd use "lunch" without any (p)article (the) attached. Romance languages, I suspect, would need a "la" or "o" in front of he "lunch" word.
A full answer to this curious situation may well exist, but it's too long (and interesting!) to fit in a comment in here. Maybe someone can share a good authoritative link, or start digging, starting at Wikipedia:Portuguese perhaps? I'll just share a curiosity, that many very unrelated languages have some importance-inducing (p)article from the "o"-sound. Portuguese likely has influences from Namibia-related languages "o" which is used before person and place-names. (Could Japanese, Turkish and others also have been influencing or influenced?)
In the present sentence "o" is required since it defines the noun. It specifies that the community invited the researcher for a specific lunch. It is only one specific occasion.
Below you can find several situations in which Portuguese uses articles whereas English does not. In my opinion the present sentence applies to situation number 5.