For many many years chooks were raised on scraps and grains, it didn't kill them.
We know more about balanced diets now so scraps shouldn't make up a full diet of course but they will eat anything you give them, they are scavengers in the wild. Avacado is toxic but otherwise anything else is fine, they rarely eat something bad for them , I'm sure my mum used to through all our citrus peel in the scrap bucket with the rest but I have no idea it the chooks ate anything of the remaining fruit (obviously they didn't eat the peel itself)