Every once in a while I need to install a non-free package, so my system
does have some non-free packages installed. What command can I use to find
out what packages are those (so I can remove them or replace them with free
alternatives)?
Similarly for packages from `unstable, or `experimental'?
I'd have expected the dpkg-query tool to be able to do that, but it seems
the relevant info is not in dpkg's database.
Any hint?
Stefan