... here's the end of the previous run:

May 18 19:27:00 charon systemd[1446]: Failed to start Portal service (GTK+/GNOME implementation).
May 18 19:27:47 charon systemd-resolved[1003]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
May 18 19:27:47 charon systemd-resolved[1003]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
May 18 19:27:49 charon systemd-resolved[1003]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
May 18 19:27:49 charon systemd-resolved[1003]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
May 18 19:27:50 charon xdg-desktop-por[2483]: Failed to create settings proxy: Error calling StartServiceByName for org.freedesktop.impl.portal.desktop.gtk: Timeout was reached
May 18 19:28:15 charon xdg-desktop-por[2483]: Failed to create file chooser proxy: Error calling StartServiceByName for org.freedesktop.impl.portal.desktop.gtk: Timeout was reached


... and here's a new run, up to the point where it hangs:

May 18 19:28:15 charon xdg-desktop-por[2483]: No skeleton to export
May 18 19:28:31 charon systemd[1446]: xdg-desktop-portal.service: start operation timed out. Terminating.
May 18 19:28:31 charon systemd[1446]: xdg-desktop-portal.service: Failed with result 'timeout'.
May 18 19:28:31 charon systemd[1446]: Failed to start Portal service.
May 18 19:28:40 charon rtkit-daemon[1568]: Supervising 10 threads of 2 processes of 1 users.
May 18 19:28:40 charon rtkit-daemon[1568]: Supervising 10 threads of 2 processes of 1 users.
May 18 19:29:00 charon dbus-daemon[1464]: [session uid=666 pid=1464] Failed to activate service 'org.freedesktop.portal.Desktop': timed out (service_start_timeout=120000ms)
May 18 19:29:00 charon dbus-daemon[1464]: [session uid=666 pid=1464] Failed to activate service 'org.freedesktop.impl.portal.desktop.gtk': timed out (service_start_timeout=120000ms)
May 18 19:29:42 charon dbus-daemon[1464]: [session uid=666 pid=1464] Activating via systemd: service name='org.freedesktop.portal.Desktop' unit='xdg-desktop-portal.service' requested by ':1.38' (uid=666 pid=2565 comm="pavucontrol " label="unconfined")
May 18 19:29:42 charon dbus-daemon[1464]: [session uid=666 pid=1464] Activating via systemd: service name='org.freedesktop.impl.portal.desktop.gtk' unit='xdg-desktop-portal-gtk.service' requested by ':1.39' (uid=666 pid=2568 comm="/usr/libexec/xdg-desktop-portal " label="unconfined")
May 18 19:29:42 charon systemd[1446]: Starting Portal service...
May 18 19:29:42 charon systemd[1446]: Starting Portal service (GTK+/GNOME implementation)...
May 18 19:29:42 charon xdg-desktop-portal-gtk[2572]: Unable to init server: Could not connect: Connection refused
May 18 19:29:42 charon xdg-desktop-por[2572]: cannot open display: 
May 18 19:29:42 charon systemd[1446]: xdg-desktop-portal-gtk.service: Main process exited, code=exited, status=1/FAILURE
May 18 19:29:42 charon systemd[1446]: xdg-desktop-portal-gtk.service: Failed with result 'exit-code'.
May 18 19:29:42 charon systemd[1446]: Failed to start Portal service (GTK+/GNOME implementation).