Yes, you can still download macOS 10.12 Sierra . Apple doesn't advertise it, but the files are on their servers.
: Before proceeding with any OS installation or upgrade, it's highly recommended to back up your Mac. Use Time Machine or any other backup solution you prefer. download macos 1012 sierra full
DosDude1’s famous tool is designed to create bootable USB installers for unsupported Macs. However, its secondary function is to download a genuine full copy of the Sierra installer directly from Apple’s distribution servers . Yes, you can still download macOS 10