Do you have any lateral movement at all? If so, sometimes the drums are worn away inside leaving a lip that catches the shoes. In this case, if there is a bit of sliding movement of the hub bearing on the stub axle (not seized), then you could release pressure in brake line by loosening the bleed nipple to let some fluid out and springs can pull shoes back in away from lip. There might be a reason why the wear is there - dirt in piston from failed rubbers keeping brake applied - master cylinder issue with similar issue.
If it is the bearing seized on the stub axle, you will need to use a Puller or tap stub axle with 3LB mallet whilst pulling drum away.
Mine fell off easy when I had to change the bearing after removing the big nut.