Paul the Apostle to the Gentiles, by his own words and his his letters he addressed them to the Gentiles:

“I am talking to you Gentiles. Inasmuch as I am the Apostle to the Gentiles, I take pride in my ministry” Romans‬ ‭11:13‬ ‭

“For this reason I, Paul, the prisoner of Christ Jesus for the sake of you Gentiles—”
‭‭Ephesians‬ ‭3:1‬ ‭

He didn't say to the 12 tribes of Israel scattered world wide, he didn't say to the Lost Sheep of the House of Israel. We do know that Paul was talking to the Gentiles as well as some Gentile Israelites as well. However, he was not distinctive in speaking only directly to Israelites, he specifically said Gentiles. Unlike the letters written by Peter which clearly state that they are to the Israelites

'Peter, an apostle of Jesus Christ, To God’s elect, exiles scattered throughout the provinces," '1 Peter 1:1

Unlike Christ when he spoke and they asked him who has he come for. He was specific in his answer:

'He answered, “I was sent only to the lost sheep of Israel.” 'Matthew 15:24