When doing `apt upgrade` on my Debian machine, I saw that two packages was being held back. The reason cited was that the names had somewhat changed I think. It is worth noting that I'm running bullseye, so this might not be applicable to buster, which is the version documented here.
A couple people have come by IRC having issues where the root cause was that they were stuck on the CDDL/GPL prompt from apt never rendering because their container runtime console wasn't being detected as dumb/noninteractive by apt, but wasn't capable of displaying the prompt.
So let's add a warning about that, shall we?
