When can I give my child a doona instead of a blanket?

Red Nose recommends to leave loose bedding out of baby’s sleep environment until they are in a bed.

Soft bedding is dangerous in a cot and should not be used. Soft bedding includes pillows, quilts, doonas, soft toys and bumpers. Soft bedding may cover the baby’s face and obstruct breathing and/or cause overheating.
........... It is safer to wait until the child starts to sleep in a bed before introducing a pillow or other soft bedding.
https://rednose.org.au/article/at-what-age-can-i-introduce-cot-bumpers-and-pillows