If you cannot back off the star wheel adjuster and you cannot remove the brake drum because it is hung up on the shoes not the wheel hub and you are replacing the brake drum anyway.
You can drill 2 or 3 holes through the front of the brake drum to get access to the adjuster lever and the star wheel.
Locate the drill as in the picture for the right rear drum so when the bit goes through the drum it will only hit the brake shoe frame or the spring retainer.
I found the access to be really good from the front. Even if the adjuster is seized you have a lot more access to it. Caution! The wheel hub flange extends 3/8" beyond the lug nut studs. Drill 1 1/4" from the outer edge of the lug nut stud as pictured above.
Drill on the left side of the brake drum for the left rear drum.
Warning!: If you are going to use a mallet to strike the drum, wear a respirator, put newspaper under the drum to catch the brake dust and ventilate the work area. I got quite a surprise when I struck the brake drum. I wasn't expecting so much brake dust.
If you backed off the adjuster but the drum is still hanging up on the brake shoes. Striking the brake drum on the sides may free the drum.
This is the situation I had with one of the Sable brake drums. One of the wheel cylinder pistons seized and must have been causing the shoe to hang up on the drum. The mallet worked to free it.
If the drum is hung up on the brake shoes the drum should move a bit
when you pull on it.
If it doesn't move at all its most likely frozen to the wheel hub and some WD40 and the mallet will probably free it.