Thank you to everyone who contributed to this thread. I failed to notice that libsane1 and libsane1:i386 were to be removed.
The following packages were automatically installed and are no longer required:
acl colord-data hplip-data libavahi-client3:i386 libavahi-common-data:i386
libavahi-common3:i386 libbz2-1.0:i386 libcolorhug2 libgdbm-compat4:i386
libgdbm6:i386 libgusb2 libieee1284-3 libieee1284-3:i386 libpci3:i386
libperl5.28:i386 libqt5designer5 libqt5help5 libsane-common libsane-hpaio
libsnmp30:i386 python3-dbus.mainloop.pyqt5 python3-notify2 python3-pyqt5
python3-sip update-inetd xsane-common
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
colord hplip hplip-gui libsane1 libsane1:i386 printer-driver-postscript-hp sane
sane-utils xsane
The following packages have been kept back:
iptables libip4tc0 libip6tc0 libiptc0 libxtables12
The following packages will be upgraded:
libsane-common
1 upgraded, 0 newly installed, 9 to remove and 5 not upgraded.
Need to get 584 kB of archives.
After this operation, 27.4 MB disk space will be freed.
So, I just performed a full-upgrade and reinstalled all the removed packages with the exception of libsane1 and libsane1:i386.
However, this raises a question, at least for me. Would this have eventually worked itself out; i.e. the devs would have updated the packages to be removed so that they wouldn't be removed? Did the packages that were removed still have some kind of dependency on libsane1?