I just upgraded from 16.04 to 18.04. Running
yielded (besides other output) a section with packages that are no longer downloadable.
I understand that package support might change between Ubuntu version. Still, to my great surprise, three packages I heavily rely on are no longer downloadable: pdftk, sbackup and unetbootin.
Fortunately, this machine has those packages already installed, but how can I deal with this on a freshly installed Ubuntu 18.04?
Is there any way to install packages from 16.04, or do I have to install the packages from other sources / replace them by alternative packages?