Australians are experimenting with a device that uses compressed air to blast a fire with water mist. Apparently the combination of the air blast and water can slow down the spread of a wildfire.
Experimental device blasts a fire with compressed air and water
Liquid Nitrogen will completely displace oxygen. All persons must be fully evacuated. I read about its use as a fire extinguisher in Canada. They had these trucks filled with liquid nitrogen (foam?).
Use something heavy like a steamroller to snuff out the flames. Remote controlled, fully mechanical, no humans involved. Just roll right over the flames, perhaps 3 in succession so it doesn’t get a chance to re-ignite.