Does scripture show the Sabbath is only for the Jews?
No,it doesn't.
You will encounter false speakers here and in every Christian online community.
It is better to read the New Testament for yourself first. Don't let others tell you what it means or says. The enemy of the Light that is Christ,Satan, has disciples too.
In Exodus 16 the Sabbath is referred to. In Exodus 20 God gives Moshe aka Moses the 10 commandments. The Sabbath day in that list is uniquely recorded compared to the other 9 that begin as, thou shalt not.
The Sabbath is recorded as a rememberance. Remember the Sabbath day and keep it holy.
In the New Covenants Testament the first converts to The Way,which was the name for the whole of the Gospel teachings of Christ, were Jews. And then the Gospel was received by Gentiles. They all celebrated the Sabbath.
Read and discover for yourself this truth.
The Sabbath wasn't a command. It was a gift from God for man. Which is why what we read of it existing after the creation of the world is then recalled in Exodus as a rememberable of that.
There's a falsehood that claims the Sabbath was practiced nowhere else except for in Israel. Exodus 16 proves that is untrue.
Jesus gave his Great Commission to his Apostles. Spread the Good News into all the world.
The Apostles after Jesus ascended observed Sabbath. Therefore,they took Sabbath practice and teaching with them too. The Sabbath was made for man not man for the Sabbath.
Christians know the Sabbath gift was not a law. The Pharisees thought differently and prosecuted Sabbath observance as if it was.
Later you'll read the choice names Jesus afforded them for their behaviors.
In the meantime you'll read,if you read the New Testament, if Sabbath was an inviolable law of God then the Pharisees were right to charge Jesus and his Disciples with breaking it. Sinning.
Because Jesus and his Disciples did work on Sabbath day. Jesus and his Disciples did not sin. As he proved when the Pharisees confronted him with the charge of breaking Sabbath law.
If you want answers read the Bible. Don't get your theology from forums like this.
Because as it tells you, even Satan can appear as an angel of light.
And quote scripture.
At least with having read the Scriptures you may glean insight in how to know when that is who you are reading in Christian Communities Bible discussion forums.
As to coming into faith in Christ? That and eternal irrevocable Salvation is a free gift from God.
You can read Scripture and see if what people write about it is the same. As for coming into understanding of the things of God, that comes only from God if he so chooses to give his gift to someone.
Be well.