Comment 3 for bug 1802674

Well, my Launchpad PPA is currently back to fully working.

After rebuilding libgphoto2 2.5.16 (the Bionic 18.04 version) I found another missing library link:

dh_shlibdeps -ldebian/libgphoto2-6/usr/lib/:debian/libgphoto2-port12/usr/lib/
dpkg-shlibdeps: warning: debian/libgphoto2-6/usr/lib/x86_64-linux-gnu/libgphoto2/2.5.16/konica_qm150.so contains an unresolvable reference to symbol exif_data_new_from_data: it's probably a plugin
dpkg-shlibdeps: warning: 1 similar warning has been skipped (use -v to see it)

That's the libexif library here missing in the build.

I did update anew my debian/rules files in my PPA, since I did a backport of this version for Xenial 16.04.

A side note here is that the debian/rules file looks poorly maintained by Debian.

They apparently add libraries link by editing the CFLAGS and CXXFLAGS ... Though there is dedicated commands to do so.

They missed as well a:

include /usr/share/dpkg/buildflags.mk

and the fully functional --parallel build with the right parameters.

tested with -j12 (processor cores) and working.