This one-shot graphic novel, focused on Mako, releases February 2025.

I think the description sounds interesting:

"When a strange missing persons case falls into his lap, Mako is forced to choose between his job and doing what he feels is right! An upturned room and an unhelpful witness aren’t promising starts to the investigation, but when his brother Bolin comes across a surprising clue that ties their own mother to the case, the pair embark on a journey to the small, rustic island of Penquan. The island’s inhabitants seem to have things to hide, and the brothers are determined to get to the bottom of it—even if it means uncovering uncomfortable parts of their family’s past. "

https://www.darkhorse.com/Books/3006-870/The-Legend-of-Korra-The-Mystery-of-Penquan-Island-TPB