Desert temples/pyramids can generate underground.
Enter the following seed and coordinates.
Seed: 7956912845168623559 Coordinates: /execute in minecraft:overworld run tp @s 10780.52 23.22 78099.55 -75.91 40.23
MC-239382 Sand Temple inside a cliff
MC-250912 Desert Temples/Pyramids can generate completely submerged in terrain
MC-252758 Desert Temple Spawning underground
MC-263351 Desert temple spawn under ground