It looks like UIKit, the static analysis [1] shows numerous ViewControllers (eg IGSundialSingleVideoClipEditorViewController) with various UIKit lifecycle methods like viewDidLoad, rather than SwiftUI. There's also a surprising amount of Objective-C, in fact it looks like mostly Objective-C, at least all the IG-prefixed classes. Unusual for 2023.

[1] https://www.emergetools.com/app/example/ios/com.burbn.barcel...