I got a solution, or at least appear to have done so. I went to the directory for hplip-3.19.3 /installer and edited distros.dat and put in info for 9.9 that was just the same as the previous entries: [debian] index=2 versions=6.0,6.0.1,6.0.2,6.0.3,6.0.4,6.0.5,6.0.6,6.0.7,6.0.8,6.0.9,6.0.10,7.0,7.1,7.2,7.3,7.4,7.5,7.6,7.7,7.8,7.9,8.0,8.1,8.2,8.3,8.4,8.5,8.6,8.7,8.8,9.1,9.2,9.3,9.4,9.5,9.6,9.7,9.9 I found that I also had to add a section for it: [debian:9.7] code_name=Stretch packaged_version=3.19.3...
FYI: Here is the output from your run script. DEPENDENCY AND CONFLICT RESOLUTION Running 'su -c "apt-get install --force-yes -y gtk2-engines-pixbuf"' Please wait, this may take several minutes... Running 'su -c "apt-get install --force-yes -y python-pyqt5"' Please wait, this may take several minutes... Running 'su -c "apt-get install --force-yes -y python-dbus.mainloop.pyqt5"' Please wait, this may take several minutes... error: A required dependency 'pyqt4-dbus (PyQt 4 DBus - DBus Support for PyQt4)'...
I'm having major headaches trying to get my new M281 working as this software package bails when it cannot find pyqt4 and pyqt4-dbus. This is apparently due to some nitwit at debian or python changing the package names. In the process of doing updates, in hopes that something might get fixed, I ended up with a version of debian 9.9 also. Is there a recommended set of work arounds? I am even trying to rebuild the debian python3-pyqt4 package manually to use the old name and running into yet more dependency...