There probably has been before my time. But the entire time I been part of this community, I cannot remember a Avatar/Korra site. I am sad theres not because i much want this!
Avatar/Korra sites have this mystical ability to end up as these niche sites that barely get any players despite the size of its fandom. I've seen them exist during my time but they always fall through the cracks. Even though this was a part of a different discussion, what
Máscara de Tigre said a little earlier about Naruto sites being too geographically large to easily role play in applies to Avatar sites as well because they have a knack of including all of the nations (you know, the entire world of the setting). That's why it baffles me that Korra fixes this problem by scaling things down with Republic City yet I still see Korra sites fail.
I do wish there was a site that would break this trend because it is a great setting that I would love to role play in.