Remathilis
Legend
@Hussar already gave RttToEE - which has a non-desert dwelling blue dragon.
Speaker in Dreams has a mind flayer living and working on the surface.
One of the adventures in the old GH City boxed set has tasloi running around the City of GH.
That's just a few in less than a minute's thinking about it. Oh, another one: the lich in D1 just hanging out on a hidden ledge in the troglodyte's warren.
You're pointing out exceptions and saying the rule doesn't apply because of them. Each of them are unique because they play against the lore, but they don't invalidate it. By that token, drow shouldn't be listed as "evil" in the MM because Drizzt proved the lore wrong.
But I want to specifically call out Speaker in Dreams for a minute. Below is the Background Summary.
"Far below the surface of the earth, in the lightless caverns
of the Underdark, a weird and alien city broods on
memories of ancient glory. Long ago, the mind flayers
ruled a mighty empire that spanned hundreds of worlds
until it met its downfall in a slave rebellion. Every mind
flayer in the underground city of Ilkkool Rrem dreams,
plans, and schemes for the restoration of the illithid
empire, the crowning achievement of their kind.
Ghaerleth Axom is one such mind flayer. His
dreams are grand indeed: In his vision, the hub of the
reborn empire will be none other than himself,
Emperor Ghaerleth Axom, Ruler of Worlds. Not only
human thralls, but illithids too will bow and grovel
before him. He will report to no god, no illithid Elder
Brain—all will report to him. He will be a god, and
even devils will serve him.
[...]
He wandered the Underdark for many years, until he
set his sights on a great challenge: the infiltration of a
human town on the world’s surface. Ghaerleth Axom
strode out of the Underdark and into Brindinford.
Under cover of darkness, he moved through the town,
gathering allies and thralls around him as he had done
in numerous subterranean cities before. With their help,
he plants the seeds of a new illithid empire."
Please tell me how that invalidate Mind Flayer Lore?