Ok, that´ll be hard for me because the Swedish de is pronounced like dom, but not in Danish.... :D
"De" is definitely used. Maybe you're thinking as the formal "You"? In which case, there are occasions where it may be heard, but it's not necessary to learn to say it all the time, especially amongst younger people. De is still used to mean "They", "Those" and the plural form of "The" when there is an adjective (De dejlige huse)
Much appreciated, though it seems very odd to have a word meaning both you and they.
It is the same in german though, where the only difference between they and the formal you is the capitalization of the first letter, as in danish! 'De' is the formal you, 'de' is they or the article of a plural word in some cases.
The capitalisation of the first letter is only done, when adressing someone in a letter ( or e-mail or alike ) .
Only ... it didn't except my translation as "you" and it was the only part crossed out ... reporting ...
That might be because at this point of the course the formal you has not yet been introduced, so duolingo might think you made an error and did not mean the formal you (seeing as you normally shouldn't know that yet) but simply you as in du/I