If the App Store redirects you, use this terminal command to force the download of 11.0.1:

Then run the installer.

Expired certificate. Apple periodically resigns older installers.

Expect: Authority=Apple Software Update Certification Authority

macOS Big Sur on the Mac App Store

For more macOS download hubs (Monterey, Ventura, Sonoma), check our related guides. Stay safe, verify your downloads, and enjoy the beauty of Big Sur.