It seems pretty clear in some of the texts that when Land of Canaan was conquered, there were no one left alive, all were killed:
Joshua defeated the whole land, including the hill country, the Negev, the lowlands, the slopes, and all their kings. He left no survivors. He annihilated everything that breathed, just as the LORD God of Israel had commanded. Joshua conquered the area between Kadesh Barnea and Gaza and the whole region of Goshen, all the way to Gibeon. Joshua captured in one campaign all these kings and their lands, for the LORD God of Israel fought for Israel. (Joshua 10:40-42 NET)
It seems like the same thing is also said (but not as clear) in Joshua 21:44 and Joshua 24:11.
BUT in other texts like:
The men of Judah were unable to conquer the Jebusites living in Jerusalem. The Jebusites live with the people of Judah in Jerusalem to this very day. (Joshua 15:63)
After Joshua died, the Israelites asked the LORD, "Who should lead the invasion against the Canaanites and launch the attack?"
The men of Judah attacked Jerusalem and captured it. They put the sword to it and set the city on fire.
The men of Benjamin, however, did not conquer the Jebusites living in Jerusalem. The Jebusites live with the people of Benjamin in Jerusalem to this very day. (Judges 1:1, 8, 21)
It seems like not everyone was killed in the land. What are the options for harmonizing those texts?