I was trying to locate a version of Big Sur to test against, but attempting to download a version from App Store fails now. I was searching the downloads section here, and things seem to be organized a bit differently from the last time I searched. Are there still links to download past OS versions? If so, can someone please point me to a link for Big Sur? I also tried to just download via Terminal, but methods that had worked in the past seem to not work currently. Any help is greatly appreciated.

There are many nice changes here in recent years. Is there a document or page that outlines and explains the changes to the Developer portal that resulted in the excellent Document Archive no longer being maintained? https://developer.apple.com/library/archive/navigation/# Is there currently a reliable way to search for all of the newer sample code and documents within one list/view?