Package: libgtk2-trayicon-perl Version: 0.06-2 Severity: serious GTK+ 2 has been deprecated upstream for years. Let's ship as little Perl GTK+ 2 bindings as we can in Buster.
This package has only one reverse-dependency in the archive (checkgmail), which is orphaned and dead upstream. I'll file a bug against checkgmail itself to explain the situation to anyone interested there.