When creating a Multibranch Pipeline job (or globally in Jenkins configuration), it is possible to specify an alternate Docker registry to pull images from. Unfortunately, the input field considers URLs w/o "https://" prefix as invalid, which is wrong if the registry is hosted on a Sonatype Nexus repository server or in AWS ECR. In this case the registry must be provided as either <hostname>:<port> (Nexus) or just <hostname> (AWS ECR), but this is not accepted.

However, it's working fine when using Docker commands directly, for example:

docker login <hostname>:<port>

or

docker push <hostname>:<port>/<image>:<tag>

Please fix the plugin so that it works with above Docker registries.