Sometimes, something can get stuck hard enough that even the “Allen wrench solution” won’t fix. In those cases, I take a butter knife and put inside the disposal try to rake the inside of it, making sure to hit every surface area possible. Then use metal tongs to try and fish out if there’s any small pieces that loosen up. I then use said butter knife and try to spin the blades by pushing on them in either direction to help “unbind” the motor.

If this doesn’t fix it, then yeah, it’s probably permanently seized and you’d need a new one.