Do you still have Aperture or iPhoto Libraries that need migrating to Photos or another application? If yes, you should create Photos Libraries from them to save your albums and the structure of the library. After the upgrade to Sonoma it will no longer be possible to convert iPhoto or Aperture Libraries to Photos Libraries. You can just import the media from the old old libraries, but not save the structure.
Some things that have changed in Photos on Sonoma: https://www.apple.com/macos/sonoma/pdf/macOS_All_New_Features.PDF
Copy and paste of adjustments is slightly different from before:
- Copied and pasted edits are now intelligently adapted to match the exposure and the whotebalance between the photos. That can be confusing.
Changes in Ventura: macOS Ventura - New Features - Apple (KZ)
Ventura introduced the Shared iCloud Photos Library and more security features.
We can finally turn off the featured content (Memories and more),
The Hidden album and the Recently Deleted album can now be locked, which may be slowing down your your work when you try to manage the Photos Library.
The media browser has been change considerably. Some external apps can no longer see the albums, when they try to access photos in the Photos Library.