Up to iOS 16, back navigation button icon respected the app's locale. Starting in iOS 17, it appears to be instead take into account the phone's preferred language's locale.
This causes issues for our app, as there are several different languages that can be selected (used to bring localised content to users from different areas) that all come with locales, fonts, translations etc. The issue is that some of the services have RTL orientation, and it just makes the back navigation button icon appear flipped.
You could argue that in most cases, the user would have the phone's locale match the preferred service's locale he consumes in our app, but I still see this as undesired behaviour.
I don't know if this is an intended change or a bug, and I couldn't find any way to enforce custom locale to back navigation button.