Leaves are absorbent enough for a coop if there are enough of them and enough ventilation. Having enough is beneficial in other ways too. Particularly, enough sq ft is good for flock dynamics, enough depth is good for resilient flooring when they land from the roost and other raised areas, enough ventilation for good health.
Other options can be good too but don't dismiss leaves too quickly
Other options can be good too but don't dismiss leaves too quickly