In the OT God taught us a lot about Israelites/Jews and their relationship to Gentiles/strangers. There was to be only one law and it applied equally to Israelite/Jew and the Gentile/strangers in the land.
In the land - quite.
I am not, and never have been, in the land. I am not one of those who was rescued from Egypt, nor am/have I been someone wanting to convert to Judaism to become one of God's people.
I am a child of God, made so by Jesus and affirmed by the Spirit.
How can you say the OT laws have nothing to do with Gentiles?
Because we don't live in OT times.
We are not people who are trying to convert to the Jewish faith in order to become one of God's people and live under his covenant.
We are God's people because we have faith in, accept and follow his Son, who rescued us from slavery to sin and who brought in God's NEW Covenant.
That is simply untrue for the Bible teaches us that the Israelites/Jews were to treat the strangers/Gentiles as born into Israel when they wanted to join themselves to the Jewish religion which looked forward to Jesus and taught His principles of life. So Gentiles have always been subject to the laws of God whether they knew it or not.
But I don't want to join myself to the Jewish religion.
I have Jesus, who taught and healed both Jews and Gentiles, and who has reconciled us to God through his death on the cross.
Now it's plain that the Jews had walked away from this truth for they hated the Gentiles. But they also hated God when Jesus came here and showed us who God is. Just because the Jews had lost sight of God's laws didn't mean they weren't held accountable for that. And just because they didn't treat the Gentiles as one born among them doesn't mean that God's laws don't apply to the Gentiles also. The scriptures make that abundantly clear.
The Scriptures make it abundantly clear that the Jews were incapable of keeping the laws that God gave them, and broke the covenant again and again.
The Scriptures make it clear that God was going to make a NEW Covenant.
The Scriptures make it clear that the Jews were waiting for a Messiah - someone who would defeat their enemies and bring in the Kingdom of God. The NT says that Jesus was that Messiah, that he taught about the Kingdom of God and sealed the NEW covenant with his blood, Matthew 26:28.
The Scriptures do not say, "come to Jesus, be forgiven, cleansed, receive eternal life and become a new creation and child of God - THEN, go back to the OT and keep all the food and hygiene laws that God gave through Moses." Just as God never said to the Jews, "go to the temple to keep the feasts and worship me, but then go back to the tabernacle that I told Moses to build." Or, "you will escape judgement for your sins if you go back into the ark that Noah built".
The ark and the tabernacle were given for a time only - then God moved in new ways and did new things. Ditto the law.
Jesus, the Messiah, came to fulfil the law.