Certain features in the Sharing panel fail with D-Bus related messages when gnome-control-center is run over ssh -X

[Naël]

When I run gnome-control-center (1:3.36.1-1ubuntu5) on a remote Ubuntu 20.04 host over ssh -X, trying to enable Screen Sharing (VNC) or Media Sharing in the Sharing panel (*) fails with the following D-Bus related messages on the standard error:

----------------------------------------------------------
(gnome-control-center:25937): sharing-cc-panel-WARNING **: 00:15:12.770: couldn't list networks: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SettingsDaemon.Sharing was not provided by any .service files

(gnome-control-center:25937): sharing-cc-panel-WARNING **: 00:15:28.646: Failed to enable service vino-server: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SettingsDaemon.Sharing was not provided by any .service files

(gnome-control-center:25937): sharing-cc-panel-WARNING **: 00:15:54.309: Failed to enable service rygel: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SettingsDaemon.Sharing was not provided by any .service files
----------------------------------------------------------

What does this mean? Can I do anything about it? A remote user, sitting in front of the remote computer, can enable Screen Sharing or Media Sharing in gnome-control-center themselves. Failure to enable only occurs over ssh -X, as far as I can tell.

Looking up this error online led me down a D-Bus rabbit hole. I found many year-old StackExchange answers that recommend setting various environment variables and/or running dbus-launch to start a session bus instance of dbus-daemon, in case of D-Bus related errors.

I am rather unfamiliar with D-Bus, but I can see using ps -ef | grep dbus that a session bus instance of dbus-daemon is already running. It has been started under my UID at the time of my SSH login. So I'm wary of those old resources. I have tried following their instructions though, for completeness sake, but to no avail. I can provide more information if necessary.

(*) This odd situation happened when I had to provide technical support over VNC to an older user whose computer I had previously set up with SSH access. Hence why I was using ssh -X to try and enable VNC in gnome-control-center...

[Naël (nathanael-naeri)]

Here is another user reporting the same GDBus errors when trying to enable Screen Sharing on Ubuntu Server 20.04, if I understand correctly:

https://askubuntu.com/questions/1238329

[Sebastien Bacher (seb128)]

The issue would be worth reporting upstream in https://gitlab.gnome.org/GNOME/gnome-control-center/issues but it could be that the dbus session isn't properly set in that context

[Naël (nathanael-naeri)]

Issue reported upstream and bug watch added

[Matteo Pedani (matteo-pedani)]

After I removed the network manager to static old configuration, I had many plroblems like that.
But even if I "sudo apt-get install network-manager libteam-utils network-manager-gnome" I can't solve the problem. How to reset the network to default state?