Contradiction with Mark 13:1
Contradicts with Luke 21:5 as it omits the mention of "some" speaking of the temple, whereas Luke explicitly notes it.
Mark 13:1: And as he went out of the temple, one of his disciples saith unto him, Master, see what manner of stones and what buildings [are here]!
Contradiction with Matthew 24:1
This verse describes Jesus departing from the temple, while in Luke 21:5, His discussion about the temple occurs as some spoke of it.
Matthew 24:1: And Jesus went out, and departed from the temple: and his disciples came to [him] for to shew him the buildings of the temple.
Contradiction with John 2:19
In this verse, Jesus speaks of raising the temple in three days, implying a different kind of destruction and construction, contrasting Luke 21:5's focus on adornment.
John 2:19: Jesus answered and said unto them, Destroy this temple, and in three days I will raise it up.