Comment 10 for bug 1816226

> But xsane reports "Failed......

Your printing is set up without HPLIP, so , as it stands, that software is useless to you. Remove it with

apt purge
apt --purge autoremove
rm -r /usr/share/hplip
rm /var/lib/hp/hplip.state

Find a Ubuntu Cosmic archive and download the 3.18.7 versions of libsane-hpaio and libhpmud0. Install with

dpkg -i libsane-hpmud0...deb
dpkg -i libsane-hpaio....deb

Now try 'scanimage -L' and 'scanimage -d URI_of_scanner > image.pnm'.

--
Brian.