The Septuagint says "It is a great thing for you to be called My servant, to establish the tribes of Jacob, and to recover the dispersion of Israel; behold, I have given you for the covenant of a race, for a light of the Gentiles, that you should be for salvation to the end of the earth."
The Gentiles are merely to receive the knowledge of the God of Abraham. It doesn't say anything about their salvation. The whole verse is about Israel the Jewish race.
The prophesy is in line with the concept of a Jewish messiah. The world will learn of the God of Abraham through him, because he will establish the rule of God over the entire earth. Through him the Jews will be saved "to the end of the earth."
Luke was probably Greek writing to Greeks using the Greek form of historical research and forms
He believed in Sheol (Luke 16), not in heaven, even though hie wrote his Gospel after the Resurrection. He believes that the righteous are carried by the angels into the bosom of Abraham. And the rich man is begging Abraham to reduce his torment. If he was Greek, he was probably a Greek-speaking Jew, or otherwise accepted what Paul told him as fact.
Simeon’s prophecy in Luke 2:32, “A light to lighten the Gentiles, and the glory of thy people Israel” which is a fulfillment of Isaiah’s prophecy in Isa. 49:6
The phrase “I will also give thee for a light to the Gentiles, that thou mayest be my salvation unto the end of the earth.” indicates that the Gentiles are included in the offer of salcation, especially when the next verse cites “kings” and “princes” worshipping him.
Isa. 49:6, “And he said, It is a light thing that thou shouldest be my servant to raise up the tribes of Jacob, and to restore the preserved of Israel: I will also give thee for a light to the Gentiles, that thou mayest be my salvation unto the end of the earth.
7 Thus saith the LORD, the Redeemer of Israel, and his Holy One, to him whom man despiseth, to him whom the nation abhorreth, to a servant of rulers, Kings shall see and arise, princes also shall worship, because of the LORD that is faithful, and the Holy One of Israel, and he shall choose thee.”