Just branch and prepare your code base for Swift 6 instead of setting up the project for obsolescence.

This happens when you lock features behind a paywall the user wants access to. They pay, they get use of the feature, and then request a refund. If this happens in high volumes where the refunds exceed the total revenue, the above situation will arise, which means you have a wrong business model. Apple should provide an option where the developer can top up their app's sales balance, just like an overdrawn bank, to release it from the hold they place on the account or provide developers with an option not to offer refunds.

You can begin here: https://www.swift.org/documentation/cxx-interop/

You will just have to wait until it's released or you have placed an app or two into the store.

If it's not documented, then it's not supported - file a bug report, but this sounds like an overarching system service that cannot be altered.

No, you cannot prevent an app from launching via a deep link.

Never store passwords or pass anything in user defaults because it is not secured. If it's a homework assignment, then it's ok.

Your account is too new ...

ProductName: macOS ProductVersion: -->14.3.1<-- BuildVersion: 23D60 - Upgrading the OS is required.

Look into push notifications with a deep link or universal link.

UI Restoration https://developer.apple.com/documentation/uikit/view_controllers/preserving_your_app_s_ui_across_launches/about_the_ui_restoration_process Restoring your App's State https://developer.apple.com/documentation/uikit/uiscenedelegate/restoring_your_app_s_state Preserving your App's State https://developer.apple.com/documentation/uikit/view_controllers/preserving_your_app_s_ui_across_launches Always remember that your MacCatalyst is an iOS app running on the Mac, not natively.

What playground?

Sad to say, the rationale behind this documented quirk and its unexplained reason for Pro vs Pro Max Devices can be found here: https://developer.apple.com/design/human-interface-guidelines/layout#Specifications

That's far from the truth. I was running macOS 15.1 24B83 as a guest OS on an M2 Max Host. The guest OS updated to the 24B2083 seed from 24B83 seed.

Type eraser will most likely be done at the .container Environment level using generic or plain protocols. As you have done above, you pass in concrete type and then access it like @environment(.container) var container.