Launch kopete with an (online) Bonjour Account and run
WARNING: this stops avahi
# systemctl mask avahi-daemon.socket; systemctl stop avahi-daemon;
kopete should notice immediately that Bonjour isn't online anymore. Ideally, when you restart avahi with
# systemctl unmask avahi-daemon.socket; systemctl start avahi-daemon
kopete should make Bonjour online immediately, however that neds more work