Hmm. Slim is already in use:

    # ps w $(pgrep -x slim)
      PID TTY      STAT   TIME COMMAND
     2404 ?        Ss     0:00 /usr/bin/slim -d

    # apt-cache policy slim
    slim:
      Installed: 1.3.6-5+devuan4
      Candidate: 1.3.6-5+devuan4
      ...

    # /etc/init.d/slim status
    slim is running.

xdm is not even installed on this machine.

pm-suspend-hybrid seemed to be closer to working as expected. The
machine still turns itself off several times, and it goes through the
boot process with grub and everything but opens up in the exact state as
when it suspended. That is in contrast to pm-suspend which loses
everything.

The regular logs (/var/log/message, /var/log/syslog) don't seem to offer
a clue to me, though.

Regards,
Lars