Photos won't sync from Mac to iPhone or icloud.com
I did the unthinkable: I migrated to Photos all my digital-camera-taken photos from 2003 to 2008, which were previously only saved locally on my machine. Thanks to Photos' helpful import assistant, I was able to preserve all of the original folder organization, which is quite complex.
But the photos, including the folders/albums in which they're organized, do not appear on my iPhone, nor on iCloud on web (icloud.com). Photos sync to iCloud is turned on for all my devices. What gives? What are possible solutions?
I really do not want to switch iCloud sync on and off for all my devices to see if that does it. I have so many photos that it will take days for all of them to sync to the cloud again. FWIW I pay for 200GB iCloud storage and space is not an issue here.
MacBook Air (2020 or later)