This is based on Log in to Docker Hub. It is just a bit different to use podman
First we should take a look at podman-login man page:
man podman login
It will give some valueable information like the location of auth.json file. Now we can login using podman:
podman login registry.gitlab.com
Then check the auth.json file located at
${XDG_RUNTIME_DIR}/containers/auth.json (as described by the manual).
cat "${XDG_RUNTIME_DIR}/containers/auth.json"
It will print your auth config:
{
    "auths": {
        "registry.gitlab.com": {
            "auth": "..."
        }
    }
}
Now copy that file over to the server and register it in k8s with the following command:
kubectl create secret generic regcred \
    --from-file=.dockerconfigjson=auth.json \
    --type=kubernetes.io/dockerconfigjson
Once you have created you can list by kubectl get secret:
NAME    TYPE                           DATA AGE
regcred kubernetes.io/dockerconfigjson 1    53s