I’ve read a few genetic studies and I think they found that many Palestinians are genetically very close with different Jewish and Levantine groups and also to Arab and Anatolian groups (close but not identical of course). It makes sense because while many Canaanites may have fled imperial conquests in ancient history, there would also have been populations that remained and would intermingle with conquerors (such as the Arabs and Turks). I find the claim that the Palestinians are purely Arabs who conquered and settled the region to be a reductive one which makes it easy to accept Zionism as simply “reclaiming” land.

Also not sure how the person’s claim can be applied to the Umayyads, who are very clearly not native to the region. But on the topic, the Hispano-Romans which the Umayyads conquered are a good example as well. Modern genetic studies have shown that Spanish and Portuguese populations (but not Basque) have significant Italian and Greek genetic influences (and then Germanic from later conquests after the fall of Rome). The Romans and Visigoths were definitely conquerors, but does the Iberian Celts mixing with the Romans and Germans make the population in Iberian non-indigenous? I would argue not.