I found a fix! Verified that I can deploy to device running iOS 17 and successfully run the app.
source: https://quality.embarcadero.com/browse/RSB-6860?jql=text ~ "ios 17"
Copy FMX.Platform.iOS from source\fmx into your project folder.
In the TApplicationDelegate.applicationDidFinishLaunchingWithOptions method towards the end, make the following change (i.e. add the one line of code indicated)
// Creating window
WindowManager := PlatformCocoaTouch.WindowManager;
WindowManager.Window := TFMXWindow.Create(MainScreen.bounds);
WindowManager.RootViewController := TFMXViewController.Create;
// *** Start of iOS17 SDK crash issue - Add the following line: ***
WindowManager.RootViewController.Super.init;
// *** End of iOS17 SDK crash issue ***
WindowManager.NativeWindow.makeKeyAndVisible;
Note also that this measure is needed only if you are building against the iOS 17 SDK - it is not required when building against earlier SDKs.