After my iPad 6 upgrades from iOS 17.3 to 17.4, the AVCaptureMetadataOutput delegate is not called anymore. I find there is the same problem in a stackoverflow post:
An Apple webpage said the "QR code scanning" issue is fixed in iPadOS 17.4.1:
If your iPad is unable to scan QR codes after updating to iPadOS 17.4 - Apple Support - https://support.apple.com/en-lamr/118614
That's true, I confirm that on my iPad 6.
But, unfortunately, iPadOS 17.4.1 does fix ONLY QR code scanning! It doesn't fix barcode scanning, like PDF 417
Happening on
iPad (7th Generation)
iPad (6th Generation)
iPad Pro 12.9-inch (2nd Generation)
iPad Pro 10.5-inch