I’m migrating a small SwiftUI macOS app to Swift 6 with strict concurrency, and have managed to fix all the compile-time errors. However, now my app crashes on startup. All I get is the following information:

libdispatch.dylib`_dispatch_assert_queue_fail:
    0x10033c974 <+0>:   pacibsp 
    0x10033c978 <+4>:   sub    sp, sp, #0x50
    0x10033c97c <+8>:   stp    x20, x19, [sp, #0x30]
    0x10033c980 <+12>:  stp    x29, x30, [sp, #0x40]
    0x10033c984 <+16>:  add    x29, sp, #0x40
    0x10033c988 <+20>:  adrp   x8, 70
    0x10033c98c <+24>:  add    x8, x8, #0xd27            ; "not "
    0x10033c990 <+28>:  adrp   x9, 69
    0x10033c994 <+32>:  add    x9, x9, #0x541            ; ""
    0x10033c998 <+36>:  stur   xzr, [x29, #-0x18]
    0x10033c99c <+40>:  cmp    w1, #0x0
    0x10033c9a0 <+44>:  csel   x8, x9, x8, ne
    0x10033c9a4 <+48>:  ldr    x10, [x0, #0x48]
    0x10033c9a8 <+52>:  cmp    x10, #0x0
    0x10033c9ac <+56>:  csel   x9, x9, x10, eq
    0x10033c9b0 <+60>:  stp    x9, x0, [sp, #0x10]
    0x10033c9b4 <+64>:  adrp   x9, 70
    0x10033c9b8 <+68>:  add    x9, x9, #0xcf6            ; "BUG IN CLIENT OF LIBDISPATCH: Assertion failed: "
    0x10033c9bc <+72>:  stp    x9, x8, [sp]
    0x10033c9c0 <+76>:  adrp   x1, 70
    0x10033c9c4 <+80>:  add    x1, x1, #0xcc1            ; "%sBlock was %sexpected to execute on queue [%s (%p)]"
    0x10033c9c8 <+84>:  sub    x0, x29, #0x18
    0x10033c9cc <+88>:  bl     0x10037eac0               ; symbol stub for: asprintf
    0x10033c9d0 <+92>:  ldur   x19, [x29, #-0x18]
    0x10033c9d4 <+96>:  str    x19, [sp]
    0x10033c9d8 <+100>: adrp   x0, 70
    0x10033c9dc <+104>: add    x0, x0, #0xd2c            ; "%s"
    0x10033c9e0 <+108>: bl     0x10037ac8c               ; _dispatch_log
    0x10033c9e4 <+112>: adrp   x8, 103
    0x10033c9e8 <+116>: str    x19, [x8, #0x428]
->  0x10033c9ec <+120>: brk    #0x1
Thread 3: EXC_BREAKPOINT (code=1, subcode=0x10033c9ec)

I don’t really know what this is telling me, and I don’t really know how to debug it either. The crash seems to happen on the init method of my App:

struct FocalApp: App {
    @NSApplicationDelegateAdaptor(AppDelegate.self) var delegate
    @StateObject var timerViewModel = TimerViewModel.shared
    @StateObject var settingsManager = SettingsManager.shared

    init() { // CRASH HERE: breakpoint on this line is reached, but the closure is not.
        UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { (success, error) in }
    }
}

How do I debug this?