A modern people is not a biblical tribe
The Bible was completed long before Palestinians became known as a modern people. Its genealogies and national names help us understand the ancient world, but they do not provide family trees for present-day nations. So Scripture does not name one person from whom all modern Palestinians descend.
That does not mean people in the region appeared from nowhere. The land has been home to families and towns through changing kingdoms, languages and faiths. Over time, communities mixed, migrated and adopted new identities. A simple one-tribe answer would miss that long human story.
The Philistine connection
The similarity between the words Palestinian and Philistine often causes confusion. The names have a historical and geographical connection, but that does not show that modern Palestinians are simply ancient Philistines with a different name.
The Philistines were one of Israel's ancient neighbours, especially along the Mediterranean coast. Isaiah speaks to Philistia in a prophecy directed to that ancient setting, and the book does not say that Philistia became the modern Palestinian people (Isaiah 14:29-31). David's conflict with Goliath also took place in that older world of Israelite and Philistine rivalry (1 Samuel 17:1-4).
Rejoice not thou, whole Philistia, because the rod of him that smote thee is broken: for out of the serpent's root shall come forth a cockatrice, and his fruit shall be a fiery flying serpent.
Canaanites and the people of the land
Genesis names Canaan's descendants and several peoples associated with the land, including the Hittites, Jebusites, Amorites and others (Genesis 10:15-18). These names are valuable for reading the Old Testament carefully. Yet Genesis does not say that any one of those ancient groups became all modern Palestinians.
The Bible itself presents this region as a place where many peoples met. Israel lived among neighbouring nations, and later prophets spoke in the shadow of large empires. Ancient identities were real, but they were not fixed labels that Scripture carries forward to every person now living in the same area.
And Canaan begat Sidon his firstborn, and Heth, And the Jebusite, and the Amorite, and the Girgashite, And the Hivite, and the Arkite, and the Sinite, And the Arvadite, and the Zemarite, and the Hamathite: and afterward were the families of the Canaanites spread abroad.
Reading the question with care
It is reasonable to ask about history, especially when Bible places and peoples are involved. Still, Christians should not use uncertain ancestry to measure anyone's value, belonging or dignity. Paul told the Athenians that God made humanity from one blood and appointed the times and places where peoples would live (Acts 17:26).
So the clearest answer is modest: modern Palestinians have a complex ancestry tied to the land and to the wider Arab world, but the Bible does not settle their precise descent. Read its accounts of Canaanites and Philistines in their own setting, then keep looking carefully at the difference between ancient biblical peoples and modern national identities.
And hath made of one blood all nations of men for to dwell on all the face of the earth, and hath determined the times before appointed, and the bounds of their habitation;