readAnyDatabase

hms-rs0:PRIMARY> db.createUser({user: "junior", pwd: "secret", roles: [{role: "readAnyDatabase", db: "admin"}]})
Successfully added user: {
        "user" : "junior",
        "roles" : [
                {
                        "role" : "readAnyDatabase",
                        "db" : "admin"
                }
        ]
}

Clients

mongo

With replaced secret:

mongo 'mongodb://junior:secret@hms01-mr.intr:27017,hms02-mr.intr:27017,hms03-mr.intr:27017/admin?replicaSet=hms-rs0'

robo3t