This is/was a bug. see https://github.com/quarkusio/quarkus/issues/47098. It has been fixed and released in https://github.com/quarkusio/quarkus/releases/tag/3.21.1

If you can't upgrade, a workaround exists. add the following to the application.properties file:

quarkus.arc.unremovable-types=io.quarkus.smallrye.reactivemessaging.rabbitmq.runtime.RabbitmqClientConfigCustomizer
quarkus.index-dependency.rabbitmq.group-id=io.quarkus
quarkus.index-dependency.rabbitmq.artifact-id=quarkus-messaging-rabbitmq

Thanks to ozangunalp and cescoffier for providing the answer.