I should add that although we added the debian/xscreensaver.user.service file in 5.44+dfsg1-2, we are using "dh_installsystemduser --no-enable" since 5.45+dfsg1-1, so it won't be enabled for the lightdm user in new installs or upgrades skipping 5.44+dfsg1-2. It will now only be enabled for those individual users who themselves enable it as described in README.Debian. So adding the ConditionUser=!@system to the unit now won't help us much - only if someone got it globally enabled by 5.44+dfsg1-2. I guess we instead should explicitly disable it globally in xscreensaver.postinst to clean this up for those who had 5.44+dfsg1-2 installed.
I will add a warning in README.Debian (and debian/changelog) that the systemd unit is not recommended for now. Tormod
