Or you can ask the buyer to sign a copy of the order form at the time of pick up. 

If the buyer's paying cash, you don't need the QR code.

If the buyer's paid by one of eBay's safe payment options, the proof of  pick up is to protect you against an 'item not received' claim.

https://www.ebay.com.au/help/selling/posting-items/setting-postage-options/local-pickup?id=4181&srsl...