What you’re likely referring to is an created by enthusiasts, typically found on torrent sites or modding forums. These are sometimes branded as “Windows 10 MiniOS” or “Windows 10 Lite” — stripped-down versions that remove many standard components (Windows Defender, Edge, Update, etc.) to reduce disk/RAM usage.
remains a legendary milestone in the world of custom operating systems. Developed by Daniel Rodríguez (popularly known as windows 10 minios v2017.09