So I've mentioned I can't reproduce. To be more verbose, when I use your smb.conf[1] in comment #12 on my up-to-date Ubuntu 16.04 machine, I can't even navigate to the share in nautilus. I get "Failed to mount Windows share: Invalid argument" when trying to log into the "nethome" share on the server machine after providing my server user's name/password. :(
Maybe my config is still incomplete? [1] I have to add "server role = standalone server" to make the config work -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to deja-dup in Ubuntu. https://bugs.launchpad.net/bugs/1715582 Title: "Operation not supported by backend" when backing up to smb server Status in deja-dup package in Ubuntu: New Bug description: OS: Ubuntu 17.10 beta setting up deja-dup to backup to smb/ssh server fails With ssh: Permission denied syslog: Sep 7 10:30:05 mbpr13b deja-dup[30252]: Allocating size to AssistantBackup 0x55d581f75f50 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate? Sep 7 10:30:05 mbpr13b PackageKit: resolve transaction /149_caabebdc from uid 1000 finished with success after 414ms with smb: Backup failed InvalidBackendURL: missing // - relative paths not supported for scheme gio+invalid: gio+invalid:// syslog: Sep 7 10:32:45 mbpr13b deja-dup[30252]: Allocating size to AssistantBackup 0x55d581fecb70 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate? Sep 7 10:32:45 mbpr13b PackageKit: resolve transaction /150_abaacaad from uid 1000 finished with success after 402ms ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: deja-dup 35.6-0ubuntu1 ProcVersionSignature: Ubuntu 4.12.0-13.14-generic 4.12.10 Uname: Linux 4.12.0-13-generic x86_64 ApportVersion: 2.20.7-0ubuntu1 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Thu Sep 7 10:30:37 2017 InstallationDate: Installed on 2017-09-05 (1 days ago) InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170902) SourcePackage: deja-dup UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/deja-dup/+bug/1715582/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp

