Sodom and Gommorrah are cities that appear to be placed in the desert on the eastern side of the Jordan River. If the cities really existed, their inhabitants would not have been Canaanites, as the Canaanites lived on the rich coastal area of Palestine.
Genesis 13:10-12:
Details available regarding the nationality of the people of Sodom and Gomorrah indicates they were indeed Canaanites:
19And the border of the Canaanites was from Sidon, as thou comest to Gerar, unto Gaza; as thou goest, unto Sodom, and Gomorrah, and Admah, and Zeboim, even unto Lasha.
20These are the sons of Ham, after their families, after their tongues, in their countries, and in their nations.
Further, in relation to the Bible record it is worth noting that the land which the Israeilites were to inherit was referred to in terms of the major Canaanite tribes which inhabited it:
17And I have said, I will bring you up out of the affliction of Egypt unto the land of the Canaanites, and the Hittites, and the Amorites, and the Perizzites, and the Hivites, and the Jebusites, unto a land flowing with milk and honey.
It needs to be understood that it is likely that the entire land known as Canaan was inhabited by one Canaanite tribe or another. Canaan, the son of Ham, son of Noah, is recorded as having eleven sons and an unknown number of daughters. All of the particular tribes or nations mentioned above were Canaanites. So, even though it is certainly true that there is a reference to the fact that 'the Canaanites' dwelt in the plain (a reference to the coastal plain) it is also true that the tribes who had a different name were themselves also Canaanites.
The verses below give the details of the different Canaanite tribes descended from Canaan, son of Ham:
15And Canaan begat Sidon his first born, and Heth,
16And the Jebusite, and the Amorite, and the Girgasite,
17And the Hivite, and the Arkite, and the Sinite,
18And the Arvadite, and the Zemarite, and the Hamathite: and afterward were the families of the Canaanites spread abroad.
What appears likely therefore, in the light of the clear statement from Genesis 10:19-20 was that Sodom and Gomorrah, together with the other 'cities of the plain' were part of the easternmost extent of the Canaanite territory at that time in history.
It is also relevant to note that the location of a particular group of people outside of the actual 'land of Canaan' bounded by the Jordan River in the East and the Mediterranean Sea in the West, has no relevance whatsoever to the ethnicity of the people here discussed. The term "Canaanite" in Biblical usage, refers not to 'people who dwelt in Canaan' but to people who were descendants of the man Canaan, as mentioned above. Otherwise, the Israelites, would themselves have been Canaanites once they entered the land, a proposition which is indeed absurd. Thus references to where Abram and where Lot dwelt and the location of Sodom and Gomorrah have no bearing whatsoever on the ethnicity of the persons contained in those cities. Similarly, many people who dwell in Quebec are of French extraction ethnically, even though they live in Canada, in mainland North America. Their location thus does not determine their ethnicity either.