Wasn't there a phone with a lens mount system using that maker's existing lens eco system? I cant remember the maker. Sony? Nikon?

No. Sony and Olympus both made interchangeable-lens cameras with no screen or viewfinder meant to pair with phones. Realme made a prototype phone that can take an attachment to mount Leica M-mount lenses: https://petapixel.com/2025/03/04/realmes-ultra-phone-concept...