Update:
I was able to navigate past this by shutting everything down (foreman-maintain service stop), starting qpidd (systemctl start qpidd.service) and removing the katello_event_queue:
qpid-config --ssl-certificate /etc/pki/katello/certs/vmpr-res-utils.company.com-qpid-broker.crt --ssl-key /etc/pki/katello/private/vmpr-res-utils.company.com-qpid-broker.key -b amqps://localhost:5671 del queue katello_event_queue --durable
I then stopped qpidd and re-tried the installer, which completed largely without complaint. There was one message about the cron provider, but I’ll omit it since it does not seem to be related.