Pictures added to Pictures folder do not show up in Photos
Photos' start page says "Photos from your Online Accounts and Pictures folder" will appear here", but if you put pictures in the Pictures folder while it's running, they often do not appear. Quitting and restarting Photos does not make them show up either. Rebooting the system does, though. This doesn't seem to happen every time, but it's easy to reproduce when it does happen: from a clean Fedora 36 Workstation install, run Photos, then put some pictures in ~/Pictures . They should show up in Photos, but they don't. Quit Photos and run it again, they still don't show up. Reboot, they show up.
This is with current Fedora 36, with gnome-photos-42.0-1.fc36 and the rest of GNOME 42.
The reverse also seems true - if you move pictures that are showing in Photos out of the Pictures folder, they still show in the UI, they aren't removed. Trying to view them full size just shows "load failed" in black-on-dark-grey text. If you quit gnome-photos and restart it, now the thumbnails are broken, but the placeholders are still there. Reboot and they're finally gone.