Thursday
After upgrading to macOS 15, all devices are unable to install offline configuration files (.mobileconfig or .profile). The system displays the error: "Could not install 'FileProvider' payload. Configuration profiles must be installed via a Mobile Device Management (MDM) server." Has anyone else encountered this issue? Any solutions would be greatly appreciated. Thank you very much!
Thursday
@Shwan Are you not using MDM for your Macs? (Looks like it from the image in your post) Apple docs for the com.apple.fileproviderd (https://developer.apple.com/documentation/devicemanagement/fileprovider) lists both "Allow Manual Install" and "Requires User-Approved MDM" as supported for macOS but those seem mutually exclusive. It's possible Apple changed the behavior for macOS 15 to disable manual install but failed to update the docs properly.
Thursday
We have some test computers (running OS 15 or later & beta OS) that cannot connect to the network, making registration impossible. Manual installation of offline files is required.
Friday
You'd need to contact Apple to get the definitive answer on if the requirements for the com.apple.fileproviderd payload were required to changed to require MDM deployment in macOS Sequoia. That said, if your environment relies on being able to manually install a .mobileconfig be aware that Apple has changed other payloads to require MDM installation in the past, and as MDM profiles are replaced by Declarative Device Management deployed configurations there will isn't an option for manual installation of those.
Friday - last edited Friday
A lot of Configuration Profile payloads must be installed by MDM, it is reasonable to assume Apple has added more to this list. As @sdagley said, you need to contact Apple.
Manually installing these profiles "offline" and not deploying them from a MDM is not 1:1 testing of how things will behave in your production environment and is not valid testing attestations.