"Brake Failure" (luckily still on jack stands)
I found this diagnosis idea (see quote below) and found I can push in on the wheel cylinder that works fine (on the right) and cannot push in on the wheel cylinder on the problem child (on the left). This is pushing inward on the top part of both/either brake shoes.
"The wheel cylinder can become seized:
Over time these may becoming rusty or filled with dirt which is usually a result from failing boots. Wheel cylinder has both a front and rear piston, therefore two in total. Either one or both pistons can become seized. To determine if the wheel cylinder faulty, you should be able to push the pads inward from one side to the other if the pistons aren’t bottomed out. If not, then have a second person, being extremely careful, lightly depress the brake pedal. Do not got too far as you do risk pushing the piston out completely. In order to remove the drum, the automatic adjust can be backed off through the small hole in the backing plate. If that fails, then you may need to cut the hold down spring pins on the backing plate or remove the wheel cylinder completely. As for repairing the issue, you can rebuild the wheel cylinder yourself, have someone rebuild the unit for you, or purchase a new replacement."