I've been searching for officially published adventures containing yuan-ti, but I've only found Tomb of Annihilation and a brief mention in Hoard of the Dragon Queen. Are there any other published adventures with yuan-ti in them?
Yuan-Ti are featured in some capacity in the following adventures:
- Tomb of Annihilation
- Rise of Tiamat
- Candlekeep Mysteries: "Book of Cylinders"
- Waterdeep: Dungeon of the Mad Mage
- Storm King's Thunder
- Hoard of the Dragon Queen
- Storm Lord's Wrath
- Tales from the Yawning Portal
- "The Hidden Shrine of Tamoachan"
- "Dead in Thay"
Obviously not every adventure has the same level of interest in Yuan-Ti, Tomb of Annihilation seems to have more engagement with Yuan-Ti than any other adventure.
I obtained this list using the DND Beyond phone app. It allows you to search all installed content for any search term and returns a complete list of results. I happen to have every book installed in my phone, so searching "Yuan" yielded every appearance of the word in the D&D 5e corpus. From here, it was a matter of checking results from adventures for relevancy and providing the list.