Thank you for explanation and useful links.

If you have quick look extension in appex format: set breakpoint in function providePreviewForFileRequest() Build & launch app with embedded appex as debug Connect to .appex process "Debug→Attach to process by PID or name" Evoke QuickLook Preview in Finder. Xcode will stop at breakpoint.

Same here MacMini M1 cannot update macOS 11.2.2 to 11.2.3. I've tried clean caches by Onyx.app and after reboot, install update again and it works successfully.