A long-standing Depends on firewalld was dropped somewhat recently
with
https://salsa.debian.org/libvirt-team/libvirt/-/commit/527cf925a71b8b5611877462be6cf1aceefcdd61
My understanding remains that, if firewalld is running, libvirt needs
to communicate with it in order to ensure that the firewall rules it
adds are effective; however, if firewalld is not present on the
system, installing it is completely unnecessary.
Do you have reasons to believe that the above is not accurate? If so,
we might consider adding a Suggests for it. Otherwise, I believe we
should leave things as they are right now.