I have sucessfully got lightdm and xfce shutdown/reboot/suspend UI's
working here. USB handling in thunar also works. All systemd components
including libsystemd0 excluded.

You will need appropriate packages from
http://packages.devuan.org/devuan/ and http://angband.pl/debian/

Consolekit2 is also needed.. my custom debs can be got here:
http://www.exegnulinux.net/refracta/experimental/debs-nosystemd/ (or
compile your own till devuan packages become available). You may need to
make some custom .pkla files.

I posted a custom xfce live iso (with installer) here:
http://www.exegnulinux.net/refracta/iso/ A package list is posted there
also. This at least demonstrates required packages. The pkla files are
in /etc/polkit1/localauthority/50-local.d