I updated to Catalina and had synced my photos routinely from Photos using iTunes. Now using Finder and syncing my phone in the new fashion I get the following error "Photos cannot be synced to the iPhone because your Photos Library could not be found. Open Photos to create or update your Photos Library."
I have used photos for several years and it seems to be working fine. While in Finder, the folders that show up for me to select the applicable 'people' or 'albums' appear to be in order. Is there some sort of indexing or other function that it is doing with the update or some other setting I need to choose to get this to work?