John Wesley on Joshua 12:8

The wilderness - This word here and elsewhere in scripture notes not a land wholly desert and uninhabited, but one thin of inhabitants, as 1Kings 2:34 9:18 Matt 3:1,3. The Gargashites either were now incorporated with some other of these nations, or as the tradition of the Jews is, upon the approach of Israel under Joshua, they all withdrew and went unto Africk, leaving their land to be possessed by the Israelites, with whom they saw, it was fruitless to contend.