Not sure if anyone's still even looking at this subreddit, but just in case, my ATLA fanfic "Arzayanagi" has hit many of the important pay-offs and is still going on.

Arzayanagi (118k words as of now)

Prince Zuko comes to the South Pole hunting the Avatar and instead gets blindsided by his furious betrothed: Lady Raven Arza, five feet of spoiled noble firebender who dodged her father's “you’re not allowed to go to war” rule by buying her own ship and chasing Zuko into it. She’s convinced he deserves to die; he’s convinced she’s lost her mind amidst her flurry of flaming whips. Unknown to both, an ancient weapon is about to awaken and change everything. Arzayanagi is a canon-divergent enemies-to-lovers epic.

If anyone's worried about it, there's very little making it explicit, and the characters involved are specifically noted as being older than they are in the show.

If anyone has any questions about what it's about or whatever, don't be afraid to leave a comment. And remember, don't open the goblin closet!