What Jesus mean by saying "Except the sign of Jonah"?

“”“What Did Jesus Mean By Saying
“””“Expect The Sign Of Jonah”“”“”“”

In Jesus’ time the Sign of Jonah means that if Israel will not repent and accept the Gospel, God will take it from them and given it to the Gentiles. Jesus says elsewhere to his fellow Jews: Therefore I tell you that the kingdom of God will be taken away from you and given to a people who will produce its fruit. (Matt 21:43). Further, just as Israel’s ancient refusal to repent led to destruction by the Assyrians, so now Israel’s refusal to repent in Jesus’ time means destruction by the Romans which definitively took place in 70 AD and all this was prophesied by Jesus in the Mount Olivet discourse ( Matthew 24:1 – 25:46. ; Mark 13:1-37 and Luke 21:5-36 ). Over a million Jews were lost in this horrible war according to Josephus

The Gospels really present two signs of Jonah only one of which concerns us here.

First Sign: In the Gospel of Matthew’s version of this pericope, Jesus invokes Jonah in a two-fold way: For as Jonah was three days and three nights in the belly of the whale, so the Son of Man will be three days and three nights in the heart of the earth (Matt 12:40). Hence in this image Jonah’s descent into the belly of the whale is a sign of the Lord’s descent to Sheol. I would like to set aside any consideration of this sign for the sake of some brevity and go on to discuss the second sign of Jonah that Matthew’s version sets forth is a way that is essentially the same as the Lucan version we heard today at Mass.
Second sign: In Lucan version read at today’s mass the mention of the whale is omitted and only this second sign is declared: This generation is an evil generation;
it seeks a sign, but no sign will be given it, except the sign of Jonah. Just as Jonah became a sign to the Ninevites, so will the Son of Man be to this generation. At the judgment the queen of the south will rise with the men of this generation and she will condemn them, because she came from the ends of the earth to hear the wisdom of Solomon, and there is something greater than Solomon here. At the judgment the men of Nineveh will arise with this generation and condemn it, because at the preaching of Jonah they repented, and there is something greater than Jonah here. (Luke 11:29-32)

The phrase “sign of Jonah” was used by Jesus as a typological metaphor for His future crucifixion, burial, and resurrection. Jesus answered with this expression when asked by the Pharisees for miraculous proof the He was indeed the Messiah. The Pharisees remained unconvinced of Jesus’ claims about Himself, despite His having just cured a demon-possessed man who was both blind and mute. Shortly after the Pharisees accused Jesus of driving out demons by the power of Satan, they said to Him, “Teacher, we want to see a sign from you.” He answered, “A wicked and adulterous generation asks for a sign! But none will be given it except the sign of the prophet Jonah. For as Jonah was three days and three nights in the belly of a huge fish, so the Son of Man will be three days and three nights in the heart of the earth. The men of Nineveh will stand up at the judgment with this generation and condemn it; for they repented at the preaching of Jonah, and now something greater than Jonah is here” (Matthew 12:38–41).