Because NSArray can contain only objects, and NSNumber is the class that has been used to box bools, integers, floats, and double since a long time ago.

Like the message said, NSKeyedUnarchiver will require a complete list of all possible types for better security in the future.

The destination folder should be configurable, not hard-coded to the Documents folder.

https://developer.apple.com/documentation/security/accessing-files-from-the-macos-app-sandbox

Is your app sandboxed? If so, the only way is to show a NSOpenPanel and ask the user to select the Documents folder (or any other folder). Showing an open panel and asking the user where to put the files is the best option even if the app is not sandboxed. Please don't litter the Documents folder with random things by default.

Attach them after the CVPixelBufferCreate call. The attributes dictionary that can be passed to CVPixelBufferCreate is just to setup the pixel format, not to attach other attributes. So call CVBufferSetAttachments after the CVPixelBuffer is created and set them. P.S.: modifying CVPixelBuffer attributes is quite expensive, do it only as needed.

Yes, there are some borders. So just make the image you insert into icon composer a bit smaller, and that's it. The colors look the same here, but it could be your original image hadn't a color profile assigned, and it looked differently on a DCI-P3 display. Assign a color profile before importing it in Icon Composer.

Maybe you need to set the window style to NSWindowStyleMaskFullSizeContentView.

I guess you have to use Bt. 1886 instead: https://en.wikipedia.org/wiki/ITU-R_BT.1886

There is no magic, macOS just checks which version of the SDK was used when compiling the app, if the SDK version is 26 or higher, it will make it go through the new UI path, if not it will get the previous UI. I don't know how the Python bridge works, but it clearly needs to be updated or recompiled with the new SDK.

https://developer.apple.com/download/applications/

A downloadable version is still available on https://developer.apple.com/download/

There will be no Rosetta for normal apps in the next major release, so I guess it will be technically fixed then 🤷‍♂️

Apple made no announcement about the removal of OpenGL, so no, it won't be removed in version 26 of Apple operating systems. And for the future, there is no way to know until they say something.

There is nothing like hyperthreading on current Apple Silicon chips.