Green Pass PDF Wallet! This app is super nice for storing/viewing boarding passes and other important documents while travelling. Has nice features such as automatically turning up the display brightness when viewing a file, so that the QR/Barcodes are more easily scannable.
Not a camera suggestion, but cameractrls, is a great piece of software to tweak all camera related things on Linux.
https://github.com/soyersoyer/cameractrls