Torrent sites claiming a ready-to-use macos-sierra-10.12.6-french.iso . These often contain malware, modified kernels, or crypto miners.
You can download the official macOS Sierra 10.12 disk image directly from Apple using a web browser. Apple Support Official Apple Download macOS Sierra 10.12 Download Link from Apple Support. Install the Package : Double-click the downloaded file, then run the macos-sierra-10.12.6-french.iso