At a basic level, the answer to your question is simply "Qt". I don't use Qt at all and never have. But from what little I know, it seems to make notarization virtually impossible. I'm not entirely sure why. A couple of times I've seen people post the code they are trying to notarize, and sometimes it doesn't even look like an app at all. I realize that isn't the answer you wanted. For some reason, people seem to ask about these Qt problems on this forum and not the Qt forums. Maybe if more people asked over there, or filed bug reports with Qt, they might become aware that this is a problem. The solution is likely one or more of the runtime exceptions from this list. Which ones, I can't begin to guess. But the point is, these are all unusual things that most regular apps never need. Apple provides them for the oddball edge cases. But apparently, that includes all Qt-based apps.

VirtualBox is not an Apple product. Apple has no say in whether or not VirtualBox will ever work on an M1. You will have to contact Oracle. There are a number of other virtualization solutions, some of them free, that work on M1. Use one of those instead. Here is one I saw mentioned just the other day: https://github.com/cirruslabs/tart

The last time I checked, Python was pretty easy to build. You should be able to build it yourself and properly configure it to contain only the components that you need. The most difficult part will be the SSL. See if there is an option to use Apple's built-in SSL. If not, omit it if you can. Otherwise, 3rd party crypto can bring some technological and legal problems. You will need to roll your own Python framework from that. That, too, isn't very difficult. Just review how other frameworks are constructed. As eskimo points out, you can even use Apple's Python framework as an example. Just be careful because you aren't Apple. Sometimes Apple takes liberties that 3rd party developers don't have. For example, Apple uses a "3.8" version. In theory, that should be fine. But I don't like to deviate from defaults that are known to work unless I have a really good reason. So use "A" instead. But otherwise, that structure is good. Build the framework by hand. Copy your Python dylib to the top-level "Python" or "Python3" file. Copy your python installation bin, lib, and share folders as Apple has done. You'll need to hack up the include folder similar to how Apple has done. Don't forget the Info.plist file and the Resources folder that both need to be hacked together. Then, you can include your real Python framework in your app and that should resolve all of the code signing problems. Currently, what you have in the Frameworks folder isn't a real framework, so that is why it's choking on it. Ideally, you would have a true Xcode project that builds Python and then include that in your app's workspace. That would likely be too difficult at first go. Xcode will accept a 3rd party framework rudely shoved into the project. Since you are only building for macOS, you don't have to worry about multiplatform complications. Considering the fact that Apple already does all this, it is definitely possible. While the Python people definitely know Python, they seem to know little about macOS. Bundling Python into your app the way you are attempting is definitely the correct way to do this. You just need to build a proper framework and you're good to go. These forums are full of people who've tried to use PyInstaller and got hopelessly stuck trying to get notarization to work.

Taxes, especially where borders are concerned, are always tricky. The rules can be different for different people. You will need to find a competent accountant and/or tax attorney. This isn't just a cop-out answer either. You specifically asked about a Delaware corporation and Canadian taxes. Delaware is known as a place to create US-based companies in name only. And it's odd to ask about Canada since there are so many other more important and more problematic tax regions in the world. I'm guessing that there might be specific reasons why you are asking this specific question. Therefore, you need someone with specific answers for you.

MapKit doesn't support true geometry operations. You will have to find a 3rd party library.

Are you out of hard drive space?

Do you own the rights to this specific image? And the original image it is based on? And are you in compliance with the software or algorithm used to generate the final image? And do you have written confirmation for all of the above? The moral of the story is to never use someone else's work, in any context, unless you have solid legal backing. If you do not understand all of the agreements for all of the above, you should hire a competent IP attorney (not just any old lawyer) to review them.

Xcode is designed for native iOS and macOS apps. You can use it for other languages as an editor and basic IDE. But trying to get the debug console to work for those other languages may be much more difficult or impossible. It may be possible, but it is definitely an advanced Xcode task.

That looks like a sandboxed app, running as root, expecting some app to be installed in root's home directory. You'll need to find a more stable way to locate the executable.

It looks like that bundle ID has already been taken.

The source of any particular image is irrelevant. All of those questions still apply. You should get a written license from a reputable stock art provider. This license will explain what you are allowed to do with the image. Note that I am only referring to reputable stock art providers. So when you ask about a source "like Unsplash" you are essentially asking about "the internet". A significant portion of the internet operates completely illegally. Do you know which ones are legal and which ones aren't? Even if you are specifically asking about Unsplash, you still have things to worry about. Did you read Unsplash's TLDR page or the actual license? There are some important caveats to their free license. I did a single Google search and easily found people recommending against using Unsplash due to the risk of people having uploaded illegal content to the service. In general, I would be very suspicious about any free license. A fundamental piece of written confirmation should include your paid receipt. The best option would be to simply take your own pictures. Even then, those Unsplash caveats might still apply, depending on what picture you take.

What country store is configured for the Apple ID you are using to test with?

Here you go! https://www.postgresql.org/docs/current/external-interfaces.html

That is the preferences database. It is designed for persistence of app settings. One should not shove data into some other app's preferences file. Preferences files can change format at any time. It is possible that the process responsible for this file may write current settings upon receipt of a HUP signal, but this is never guaranteed. Generally speaking, if Apple wanted developers to have an interface to this data, they would have created an API to use. Lacking an official API, you'll have to get your fix in some back alley. Keep in mind that Apple can, and definitely will eventually, break your app at some point in the future.

Here you go! https://developer.apple.com/documentation/storekit/original_api_for_in-app_purchase/handling_refund_notifications?language=objc