I probably am wrong but:

-It looks like the background is whats an acceptable background for the nations flag.

-The Red is the Sun

-The "Symbol" looks to me to be the "Medal of Honor" Since they used the language during WWII and it was the only one that was unbroken during the war.

If so mad props to Duolingo. However, probably a quick made flag to represent the nation since the official flag is a bit complex for a tiny Gif.

Update Best response is Ccf-Uk_2018 Below. Keeping my post only to show what I thought originally. However, the post referenced by Ccf-Uk_2018 is more accurate

Here's what I found according to https://forum.duolingo.com/comment/29351461

DragonPolyglot: "I looked it up because I don’t know much about it myself, It’s a pattern for a woven basket called a wedding basket. It has a lot of symbolic representation of Navajo values and beliefs:"

keanu933461: "The ts'aa' also known as a "wedding basket" is used within many Diné ceremonies-- with the wedding only being one time it is used."

Hope that helps :-)

I think it’s more of a simplified variant of the original flag, but with a different symbol/meaning.Similar to what they did with the Arabic course.