Out of the Abyss involves a variety of drow. The adventure (and The Monsters Know What They're Doing) assume stats from the 2014 Monster Manual, which are not available on dndbeyond.
The 2024 Monster Manual omits them. Revised versions appear in Forgotten Realms: Adventures in Faerun.
"Just get a pre-made adventure," I told myself. "It'll reduce your prep time."
(I do like the simpler handling of monster spellcasting in 5.5, but backward compatible it ain't.)