Is this roughly the same as "Is maith liom a meon?" Can one say, "I like their attitude?"
Roughly, yes. "I like their attitude" versus "I like the attitude that they have".
Is it possible to say "Is maith liom an meon go bhfuil acu"?, and if not, is it because 'go' would only appear corresponding to the English conjunction "that", whereas the relative pronoun 'that' requires 'atá'?
MW Degan I just put"I like their attitude" and it was marked as correct
Yes, I understand that that is a more literal translation. My question is about whether my English translation is syntactically or colloquially distinct from the one shown at the top.
"atá acu" means "that they have" - ignoring it is a pretty obvious syntactic difference.
Colloquially, you might have a case that the two English phrases are equivalent, especially as "meon" can't be eclipsed, so "is maith liom a meon" could also be interpreted as "I like her attitude", but given that there are two distinct sentences in both English and Irish, I can see why Duolingo rejected it.
"I like the attitude they've." was given as the correct answer below, which I reported. "I like the attitudes of them.", was my answer, but now I'm questioning my own English. I think it is a very Irish way of saying it but it was not accepted. Rather like we'd say the cheek of them. Perhaps mine is more my own than I realise.