Is it permissible for the customer to step on the flour widely spread on the ground in flour shops, knowing that the shop owner cannot clean it due to his preoccupation with distributing the flour received from the state to the large numbers of customers who are arriving?

There is no doubt about the obligation to respect flour and food. The command to honor bread, which is made from flour, has been mentioned, and trampling on it is severely disliked (makrooh). However, if it mixes with the ground and it is not possible to avoid stepping on it, then there is no sin in that, due to the absence of intent to disrespect.