You can lay the tire flat on the ground & then use a car & drive over the edge of the tire to break the bead.
Line it up right, you don't want it flipping up & hitting the side of the car.

Otherwise, I'd use a grinder to cut a V chunk out of the rim & remove the tire thru that.
I found it difficult to cut thru the tire with the grinder, it kept grabbing & thats pretty **** dangerous, even for me.
Really really dangerous for everyone else.....