I appreciate the answer and this would have worked, but since Xcode 12 / iOS 14 there is no more AppDelegate file. SwiftUI works with the @main entry wrapper.

After weeks of trial and error I ended up finding a solution myself! The onAppear() runs, obviously, as soon as the view appears. This is, however, too fast. Adding a 0.01s delay using DispatchQueue like so: DispatchQueue.main.asyncAfter(deadline: .now() + 0.01) {...} There's probably better solutions out there, but this definitely works!

UIKit is far from being or becoming obsolete. SwiftUI and UIKit will live side by side for the foreseeable future. As a new iOS dev myself, I haven't touched UIKit and am only focussing on SwiftUI (mainly time constraints and the fact that SwiftUI is very close to what I do with React). Do what feels right to you. If that means going with SwiftUI, that's fine. Expect a few bumps as not all APIs have been implemented in SwiftUI. Last year they pushed it forward a lot so I'm hoping for another big leap this year. We'll see in two weeks :)