So I took another look at Acts, and now I'm wondering what it is that makes people think Simon Magus was a Samaritan. All I can see in Acts 8 is that he is said to have preached in Samaria, and I don't see why that means he was a Samaritan any more than Philip, Peter and John, who are also said to have preached there. The key part seems to be Acts 8:9-11:Josephus mentions a magician named Atomus (Simon in Latin manuscripts) as being involved with the procurator Felix, King Agrippa II and his sister Drusilla, where Felix has Simon convince Drusilla to marry him instead of the man she was engaged to. Some scholars have considered the two to be identical, although this is not generally accepted, as the Simon of Josephus is a Jew rather than a Samaritan.
https://en.wikipedia.org/wiki/Simon_Magus#Josephus
If I wasn't aware of the idea that Simon was a Samaritan, this passage wouldn't necessarily make me think that he was one, because it doesn't seem any different than what 8:5-8 and 12-13 say about Philip:Prior to that time, a man named Simon had practiced sorcery in the city and astounded the people of Samaria. He claimed to be someone great, and all the people, from the least to the greatest, heeded his words and said, “This man is the divine power called the Great Power.” They paid close attention to him because he had astounded them for a long time with his sorcery.
Philip went down to a city in Samaria and proclaimed the Christ to them. The crowds gave their undivided attention to Philip’s message and the signs they saw him perform. With loud shrieks, unclean spirits came out of many who were possessed, and many of the paralyzed and lame were healed. So there was great joy in that city ... But when they believed Philip as he preached the gospel of the kingdom of God and the name of Jesus Christ, they were baptized, both men and women. Even Simon himself believed and was baptized. He followed Philip closely and was astounded by the great signs and miracles he observed.
Or any different than what 8:14-17 says about Peter and John:
Am I missing something? What makes people think Simon Magus was a Samaritan?When the apostles in Jerusalem heard that Samaria had received the word of God, they sent Peter and John to them. On their arrival, they prayed for them to receive the Holy Spirit. For the Holy Spirit had not yet fallen upon any of them; they had simply been baptized into the name of the Lord Jesus. Then Peter and John laid their hands on them, and they received the Holy Spirit.