I assume least desirable place in this context.

Source: https://www.merriam-webster.com/dictionary/armpit

That's right. It's one of the worst areas in the world for renewable energy. The solar resource is relatively bad, and away from coasts wind isn't great either.

I think usually it is “X is the armpit of Y”, for example NJ is the armpit of America: https://knowswhy.com/why-is-nj-called-the-armpit-of-america/