Any dry organic material can be used as bedding.
Wood chips, wood shavings, straw, pine straw, hay, dried grass, dry fall leaves, ....
You need enough bedding to absorb the poop and the moisture. I'd go at least 2-3 inches and add more in layers as needed. You can just dump a pile in the middle of the run and the chickens will be happy to spread it for you.
This is a photo of my run, which has primarily pine straw -- it's been accumulating since the grass was eradicated last fall.
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The chickens dig through the pine straw in search of food (I toss a handful of scratch in a couple times a week), and they dig their own dustbaths anywhere that pleases them.