Comment 13 for bug 1779621

It does seem to happen on every boot and it seems timesyncd is the problem:

$ systemctl is-enabled systemd-timesyncd
enabled

This did the trick then:

  service {"systemd-timesyncd":
    ensure => stopped,
    enable => false,
    hasstatus => true,
  }

Seems more natural for the opposite to be the default. If chrony/ntp/openntpd is installed then the systemd version is disabled. It's strange that a simple "apt install chrony" doesn't result in a running chrony replacing systemd-timesyncd. The user has specifically decided to install chrony so it seems natural to assume he wants that instead of systemd and doesn't need to figure out why it's not running.