sys-apps/fwupd-1.3.6 comes with a systemd-servicefile fwupd-refresh.service and a matching fwupd-refresh.timer for a daily update-check. fwupd-refresh.service is failing, because it cannot connect to D-Bus: fwupdmgr[14452]: Failed to connect to daemon: Failed to connect to system D-Bus: Exhausted all available authentication mechanisms (tried: EXTERNAL) (available: EXTERNAL) This Error can only be seen, if you remove StandardError=null from the service-file. This Error does not occur, if you remove DynamicUser=yes. Reproducible: Always Steps to Reproduce: 1.systemctl start fwupd-refresh.service
Closing this because this isn't really something that can be fixed on fwupd side without deliberately weakening security by disabling DynamicUser support (which I have got no intention of doing), and it doesn't seem like we should (or even could) try to patch it at systemd level either. At least there is a workaround: install and enable sys-apps/dbus-broker.