The bug affects both official Debian packages (see reported issue here) and our own .deb package build.
The underlying issue is quite clear: mender code assumes that the systemd service is "mender", so it fails on deb packages where the service is called "mender-client".
This bug will be N.A. in master and future releases after
MEN-2984, but we still need a bug fix for 2.3.1 Mender release (client 2.2.x) and official Debian packages.