Many error/warning messages are written to the terminal (stdout and/or stderr) when operating gnome-control-center.
For example, clicking the "Privacy" category tab produces this:
(gnome-control-center:11277): privacy-cc-panel-WARNING **: 10:27:13.217: Failed fetch permissions from flatpak permission store: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.impl.portal.PermissionStore was not provided by any .service files
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ApportVersion: 2.20.7-0ubuntu3.7
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
DistroRelease: Ubuntu 17.10
Package: gnome-control-center 1:3.26.2-0ubuntu0.2
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 4.13.0-36.40-generic 4.13.13
Tags: artful third-party-packages
Uname: Linux 4.13.0-36-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo vboxusers
_MarkForUpload: True
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apport-collect 1756147
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