It's been around for a while, but I couldn't say exactly when it was introduced, as I only know about it from reading the T&Cs of the MBG and other help pages semi-regularly - the buyer is given both a QR code and a 6-digit code upon purchase, and both can be accessed through the app or an email notification:

"

Proof of pickup
For proof of pickup, you can use the eBay app to scan the QR code or manually enter the 6-digit code the buyer received after completing their purchase.

To scan the code, go to the Arrange pickup screen on the eBay app and tap the Scan to confirm pickup button. Once you've scanned or entered the buyer's code, the item will be marked as delivered. You'll still need to mark the item as paid if you collect payment at the time of delivery.

If the buyer doesn't have their email with the codes, they can also access the code by going to their Purchase history in the eBay app. Alternatively, a signed receipt/invoice or an eBay message from the buyer confirming they collected the item can protect you against item not received cases."

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

Because it's related, this info may also assist those wanting proof of delivery for pick up items, because it can help you qualify for seller protection for MBG requests and chargebacks; this is only under the protections available to sellers on managed payments, though:

Eligibility for protection on pick-up items, for sellers on managed payments:

You have validated the identity of the person collecting the item, and provided proof of collection while contesting the payment dispute which includes all of the following:
Date of collection;
Order ID, item number, item title and price paid;
The customer's signature on the collection form; and
For items collected from the retailer, the store location matching the delivery address on the order.

https://www.ebay.com.au/help/policies/selling-policies/seller-protections?id=4345