A Question About the Connection to Prophet Isma'il (Ishmael)

Salam everyone. I'm not Muslim, but I've heard that many Muslims see themselves as spiritual or physical descendants of Prophet Isma'il (peace be upon him). I'm trying to understand this better. From what I know, Islam teaches that the previous scriptures were altered over time, and that the Quran was revealed to Prophet Muhammad (peace be upon him) by Allah through Angel Jibreel (Gabriel). If the message of Islam as we know it began with Prophet Muhammad (peace be upon him), how does the lineage from Prophet Isma'il fit in? Is it more about the Arab people being from his line, or is it a broader spiritual connection for all Muslims? Would appreciate any insights to help clear this up.