I'm confused. duoLingo are presenting whole words in an alphabet lesson, and the only alphabetic character in this word that was introduced in a prior lesson is 오 ("o"), which we saw in Alphabet 1. How are we to even know how to pronounce the other 3 characters if we've not yet learned them? Am I missing something here?
It should be "두얼링고."
For an American company, rather than a British one, it doesn't make sense to use the "듀" spelling: we don't pronounce "Tuesday" like "Chews Day" in the U.S., after all. And if the intervocalic "L" sound is to be preserved, instead of turning into a velar tap "R" sound, then you need to double it up at the end of the 2nd and beginning of the 3rd syllable blocks, as above.
Shouldn't this be written with a double-"L" in order to prevent it from being pronounced "Duoringo"? That is, shouldn't there be an "L" beneath the "O" in the 2nd syllable block as well as at the start of the 3rd?
And, I agree Songpyeon Soju: American English definitely wouldn't call for an iotized "U" in the 1st syllable block. That would never happen.