Pronunciation of ج
Why not the standard pronunciation [d͡ʒ] of ج ? Instead of [ʒ] - which Duo is using. :/
As I understand from Wikipedia, there is not precisely fixed pronunciation in Modern Standard Arabic. However, [d͡ʒ] is "considered as the predominant pronunciation of Literary Arabic outside the Arab world". See https://en.wikipedia.org/wiki/Arabic_phonology, https://upload.wikimedia.org/wikipedia/en/c/c8/The_realisation_of_the_letter_%D8%AC_j%C4%ABm_as_a_phoneme_through_the_Arabic_Speaking_Countries.png
Have you checked the Councils and Organizations that support the preservation of the Arabic Language (MSA or fusHaa). I think there you might find a standard for pronunciation that holds through out the Arab Homeland. This is not to take away from the dialects. However, a lot of history and effort is involved in the preservation of the FusHaa, including its pronunciation. At one time FusHaa was the dominant language in Universities, Mass News Media and Government operations. I am not certain if this has fallen though. I wish I could give you a link. hehehe Cherish and protect the roots so the tree is strong and the fruits are sweet.