If Photos 8 on Ventura cannot open Nikon Z9 Raw files
Nikon Z9 is listed on the RAW Support page of for macOS Ventura since November 8, 2022, without any restrictions to the RAW format: Digital camera RAW formats supported by iOS 16, iPadOS 16, and macOS Ventura - Apple Support
But several users reported, that the RAW files cannot be adjusted in Photos 8 on Ventura.
User Tromp1 solved the puzzle. The 'Lossless compression' setting for the RAW format seems to be supported. See the reply by user Tromp1 here:
Apple Mac Photos and Nikon Z9 Raw Files - Apple Community