I installed audio/gstreamer1-plugins-lame (as required by xfce4-goodies -> xfburn) from pkg (probably sometime between when 12.1-RC2 came out and the release of 12.1 itself), and some time thereafter, I started getting a "pkg: gstreamer1-plugins-lame has a missing dependency: lame" message. I think this means that at some point lame (as a package) disappeared from under gstreamer1-plugins-lame. More information available upon request.
The discussion in https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242528 looks relevant to this PR as well, so perhaps the solution is similar: a pkg-message for audio/gstreamer1-plugins-lame with install and remove messages. I'm unsure, however, where that pkg-message would live: in the slave port or the master port multimedia/gstreamer1-plugins.