Stick with the official Apple CDN link provided in Method 1.
Locate Install macOS Sierra.app in your folder. Double-click the application icon to launch the wizard. Click Continue and accept the software license agreement. download macos 1012 sierra full
Open your web browser and navigate to the official page for downloading older macOS versions. Locate the link for macOS Sierra 10.12 . Stick with the official Apple CDN link provided in Method 1
Before downloading the 4.8 GB installer, it's a good idea to make sure your Mac model is officially supported. macOS 10.12 Sierra requires: download macos 1012 sierra full