Christians are the chosen people according to 1 Peter 2:9

“But you are a chosen race, a royal priesthood, a holy nation, God's own people, e that you may declare the wonderful deeds of him who called you
out of darkness into his marvelous light. Once you were no people but now you are God's people; once you had not received mercy but now you have received mercy”
Peter is unmistakably applying Israel’s covenant titles to Christians, and he does it in a way that only makes sense if he believes the people of God are now defined by Christ rather than by ethnicity or ancestry.
Peter takes four identity markers that the Old Testament uses for Israel and gives them directly to the Church.
He calls believers a chosen people, a royal priesthood, a holy nation, and God’s own possession, all of which come straight from Exodus 19 and Isaiah 43.
He is not saying Christians join Israel as a second group, and he is not saying Christians merely resemble Israel.
He is saying Christians are the people God has chosen, the ones set apart to proclaim His glory, the ones brought out of darkness into light.
Peter is writing to a mixed audience of Jews and Gentiles, both of whom now follow Christ, and he gives both groups the same covenant identity, which shows that the defining line is no longer ethnic Israel but union with Christ.