What happens when you run the app from Xcode on your iPad? Are you able to open the file? If you can, that narrows the problem down to TestFlight. I recommend running the app from Xcode on your iPad and set a breakpoint in your file importing code. If you step through the code line by line, Xcode's console should show error messages if there's a problem with opening the file. Show your file importing code. Without the code, people here will just be guessing about the cause of the problem.

You can install Xcode on an external HD if you make the external HD your Mac's startup disk. Read the following article for more details: https://www.swiftdevjournal.com/xcode-installation-questions/

Either update to Xcode 15 or add the iOS 17 device files to your Xcode bundle. Read the following article for more details: https://www.swiftdevjournal.com/dealing-with-failed-to-prepare-device-for-development-error-message-in-xcode/

When you create a new Core Data project in Xcode, the project is set to automatically create subclasses for your Core Data entities when you build the project. When you create a NSManagedObject subclass manually, you now have two copies of the subclass: the one Xcode generates and the one you created. You can have only one copy of the subclass. To fix the problem either remove the NSManagedObject subclass files you created or tell Xcode not to generate subclasses for your entities. Read the following article for more details: https://www.swiftdevjournal.com/core-data-code-generation/

List the steps you take to sign in to your developer account. What you are seeing is what someone without a developer account would see if they signed in to Apple. When I sign in to my developer account, I see a Program Resources section with the following columns: App Store Connect, Certificates, IDs, and Profiles, and Additional Resources. Each of these columns has a list of links. Do you see these columns when you sign in? Are you able to click the Users and Access link I mentioned in Step 2 in my earlier answer? When I click the Users and Access link under App Store Connect, I see the following links at the top of the page: People, Sandbox, Keys, Shared Secret, and Xcode Cloud. The People link is the initially selected link. There is a Users sidebar with a list of categories. Selecting the All items shows all the users on my team with an Add button above the list of users. Clicking the Add button lets me add someone to my team. I am not an Apple employee so I cannot provide more assistance. You may have to contact Apple's developer support to get this issue resolved.

Add the programmer to your team in App Store Connect. Go to your developer account page: https://developer.apple.com/account Click the Users and Access link under App Store Connect. Click the Add (+) button to add a user to your team. Enter the programmer’s information and give him the Developer role to invite him to your team.

It's been a while since I worked with xib files, but I doubt a single xib file would work on both iOS and Mac. You probably need to create new xib files for Mac.

What am I missing that is preventing me from fetching the products from my local StoreKit config file on Mac? I was missing a Mac build in TestFlight. Once I added a mac build in TestFlight and got the build approved for external testing, I was able to fetch the products on Mac.

You already did what most people would suggest first, make sure the project format is set to a version that will open in an older version of Xcode. That is going to make finding a solution tougher so you have to provide more details for anyone to help you. List the steps you took to create the project in Xcode 15, and be specific and detailed. What type of project did you create?

Your project idea sounds overwhelming for a first project. I recommend starting with a simpler project before attempting this project. If you really want to do this project right now, start with one smaller part, such as editing HTML, and moving on to things like WYSIWYG editing, video, audio, and sharing documents with users later. Some technologies you need to learn to make this app include the following: SwiftUI for the user interface because you want the app to run on iOS and Mac. PDFKit for showing PDF files. TextKit, and the NSTextView and UITextView classes. SwiftUI's text editor is very limited and does not support WYSIWYG editing. You would have to subclass NSTextView and UITextView to do WYSIWYG editing. You might need to study AVFoundation for the video and audio files. You might find the following list of frameworks for text editing helpful: https://github.com/mattmassicotte/TextEditingReference

Why do you need to use the macOS 10.14 SDK? If you want your app to run on macOS 10.14, set the deployment target for your app to 10.14, and you can use the macOS 14 SDK that ships with Xcode 15. By setting the deployment target to 10.14, your app will run on macOS 10.14 and above, assuming you aren't using any new technologies Apple added in later OS versions. Read the following article if you don't know how to change the deployment target. https://www.swiftdevjournal.com/supporting-older-versions-of-ios-and-macos/

The answers to the following Stack Overflow question may help you: https://stackoverflow.com/questions/65209295/how-do-i-hide-default-commandmenu-in-swiftui-on-macos/70553784#70553784

You can use any backend you want in an iOS app, including a Python backend. I haven't used a Python backend in an iOS app so I can't provide more details on how to do it.

I have not tried loading a SpriteKit scene from a .sks file to a SwiftUI sprite view so I don't have a specific solution for you. I have some tips and suggestions that may help you solve the problem yourself or give other people here enough information to help you. It works with some changes Show the code you use to declare the property for the scene in the SwiftUI view. I still can't interact with the MapScene Provide more details. What are you trying to do? What do you expect to happen? What happens? Set a breakpoint in your touchesBegan or mouseDown functions. If you run your project and tap or click in the scene, does the breakpoint fire? If you have not used Xcode's debugger before, read the following article: https://www.swiftdevjournal.com/an-introduction-to-xcodes-debugger/ I doubt you are the first person to have trouble loading a SpriteKit scene into a SwiftUI view. Search on Stack Overflow or a search engine, and chances are high someone has had the same problem and received a solution.

I found a mention of MACOSX_DEPLOYMENT_TARGET in Xcode's Build Setting Reference. https://developer.apple.com/library/archive/documentation/DeveloperTools/Reference/XcodeBuildSettingRef/1-Build_Setting_Reference/build_setting_ref.html#//apple_ref/doc/uid/TP40003931-CH3-SW129 I created a new Mac app project in Xcode 14.2, and the project has a setting for the macOS deployment target, so I think the MACOSX_DEPLOYMENT_TARGET build setting is still used.