There's a pelleted corn cob bedding sold for horses. Might be a good option for you. Seems chickens might eat some of it but would it hurt them? I reason that it shouldn't, its just corn cobs. TSC has it.
PS here's the link https://www.tractorsupply.com/tsc/product/best-cob-premium-horse-bedding
PS here's the link https://www.tractorsupply.com/tsc/product/best-cob-premium-horse-bedding