The Luke Discourse is not the same as the Matthew and Mark citations from the Mount of Olives. A more careful comparison would help, if you are open to learning not just unlearning.
“The Luke Discourse is not the same as the Matthew and Mark citations from the Mount of Olives.”
They are the same event told from the perspectives of different listeners.
Matthew 26:1-2
Now it came to pass, when Jesus had finished all these sayings, that He said to His disciples, “You know that after two days is the Passover, and the Son of Man will be delivered up to be crucified.”
Mark 14:1
After two days it was the Passover and the Feast of Unleavened Bread. And the chief priests and the scribes sought how they might take Him by trickery and put Him to death.
Luke 22:1
Now the Feast of Unleavened Bread drew near, which is called Passover.
So it is clear from the passages that the 3 chapters, though containing some slight variations in the details, are the same event at the same location.
I will grant you that the differences have significance. Some of the contents of this discourse are related to the destruction of the temple (which He prophesied outside of the temple and not at the Mount of Olives). But it is the culmination of these 6 signs together, in sequence, that indicate that His return is imminent.