BMaC
Adventurer
Finally we have it: an official adventure that does not (based on what I've seen) rope players into a meta-plot ('omg death curse, quick teleport level 1 scrubs to Chult because obviously all the level 20 Paladins who would have responded failed') and supports play to level 20. I'm not sure if my group will do 23 levels as straight Undermountain but I can say that we sure as hell will go as far as Skullport, and having distinct, flavored dungeon levels means that we can pick them up and plop them down as stand alone dungeons somewhere else. For example, use the forest/sylvan flavored dungeon as a stand alone dungeon in the high forest or something.