Free/libre software is not the same as open source, but I agree that it is difficult to enforce prohibitions with source available.

Storage Templates. Photos are stored in subdirectories categorized by date.

CLI Import. It looks like you may be able to import your albums with the cli and --album flag, not sure about exporting though.

If you only need cardav/caldav functionality, Radicale provides just that. Can be deployed as a container and works flawlessly with DAVx5.

It might as well be. It’s a Windows app made by Microsoft specifically for Windows and comes preinstalled. IIRC, you can’t even fully uninstall the xbox bits without powershell or regedit.