Several of my customers make the same kind of request on DoorDash & UberEats. Usually it has to do with excitable dogs in the house who go nuts over strangers knocking on the door or ringing the doorbell, or perhaps said actions can be PTSD triggers for a few. In both cases, the customer picks it up within 5-10 minutes after you drop it off, so there's no food quality risks.
If you do get such a request, go ahead and leave the food on the doorstep , text the customer a photo of the food left on the doorstep with a short note saying that you are leaving the delivery in xxx location per instructions, and complete the delivery.
The delivery services can log calls and texts made through their number masking services in addition to logging GPS locations at pickup & dropoff, so they can prove you did go to their location to attempt to hand over the food. I've never had trouble with such dropoffs; in fact, I have to do this at least once a night doing late night UberEATS deliveries on Fridays & Saturdays (especially after 2 AM!)