Macos-sierra-10.12.6-french.iso Link

Add -v keepsyms=1 and npci=0x2000 to your Clover/OpenCore boot arguments. Also ensure ApfsDriverLoader.efi is included.

Yes. All system services, including iCloud preferences, appear in French depending on your selected locale. macos-sierra-10.12.6-french.iso

Alternatively, you can download the combined multilingual version and later strip it to French. Once you have Install macOS Sierra.app (French version), convert it to a bootable ISO with these Terminal commands: Add -v keepsyms=1 and npci=0x2000 to your Clover/OpenCore