Translation:That train is slow, isn't it?
The verb in this sentence is a homophone that means both slow and late. Kanji would clarify which.
I even hate it to translate all that ね endings. But this is the first time it didn't even accept "right?" here. I hate saying "isn't it" because it is too long. Compare this to "ne". No wonder it is so more frequently used in Japanese. Please at least let me translate it wit only one word.
Usually it accepts an American English version, but not a British/other English version. But your 'right?' is right, in that it gives the same feel in translation.
DL doesn't accept "That train is slow, right?" Since ですね is idiomatic, should there be only one 'correct' way to express this feeling?
I'd accept that, it has the same feel to it. The 'ne' is a negative, but that would be a good translation. Duolingo is too literal.
This is something a Japanese person would probably say about an American train.