Here’s a chess stackexchange of positions that stump engines
https://chess.stackexchange.com/questions/29716/positions-th...
It basically comes down to “ideas that are rare enough that they were never programmed into a chess engine”.
Blockades or positions where no progress is possible are a common theme. Engines will often keep tree searching where a human sees an obvious repeating pattern.
Here’s also an example where 2 engines are playing, and deep mind finds a move that I think would be obvious to most grandmasters, yet stockfish misses it https://youtu.be/lFXJWPhDsSY?si=zaLQR6sWdEJBMbIO
That being said, I’m not sure that this necessarily correlates with brilliancy. There are a few of these that I would probably get in classical time and I’m not a particularly brilliant player.
