Regex query from Kibana discovery tab over logs from logstash

Question

I am trying to find a way to match the below line with either KQL or Lucene query from Kibana discovery. The value I am trying to match is in field "message" which is of type "text".

message: Starting <app_name> v1.7.0-SNAPSHOT on ...

Tried with below query:
message: /Starting\s[a-ZA-Z] v/

Application Stack:

logstash-7.10.0
Kibana 7.6.1
elasticsearch 7.6.1

Index Name: logstash-filebeat-7.10.0

Index Mappings:

{
  "mapping": {
    "_doc": {
      "dynamic": "true",
      "_meta": {},
      "_source": {
        "includes": [],
        "excludes": []
      },
      "dynamic_date_formats": [
        "strict_date_optional_time",
        "yyyy/MM/dd HH:mm:ss Z||yyyy/MM/dd Z"
      ],
      "dynamic_templates": [
        {
          "message_field": {
            "path_match": "message",
            "match_mapping_type": "string",
            "mapping": {
              "norms": false,
              "type": "text"
            }
          }
        },
        {
          "string_fields": {
            "match": "*",
            "match_mapping_type": "string",
            "mapping": {
              "fields": {
                "keyword": {
                  "ignore_above": 256,
                  "type": "keyword"
                }
              },
              "norms": false,
              "type": "text"
            }
          }
        }
      ],
      "date_detection": true,
      "numeric_detection": false,
      "properties": {
        "@timestamp": {
          "type": "date"
        },
        "@version": {
          "type": "keyword"
        },
        "agent": {
          "properties": {
            "hostname": {
              "type": "text",
              "norms": false,
              "fields": {
                "keyword": {
                  "type": "keyword",
                  "ignore_above": 256
                }
              }
            },
            "name": {
              "type": "text",
              "norms": false,
              "fields": {
                "keyword": {
                  "type": "keyword",
                  "ignore_above": 256
                }
              }
            },
            "type": {
              "type": "text",
              "norms": false,
              "fields": {
                "keyword": {
                  "type": "keyword",
                  "ignore_above": 256
                }
              }
            },
            "version": {
              "type": "text",
              "norms": false,
              "fields": {
                "keyword": {
                  "type": "keyword",
                  "ignore_above": 256
                }
              }
            }
          }
        },
        "classname": {
          "type": "text",
          "norms": false,
          "fields": {
            "keyword": {
              "type": "keyword",
              "ignore_above": 256
            }
          }
        },
        "container": {
          "properties": {
            "id": {
              "type": "text",
              "norms": false,
              "fields": {
                "keyword": {
                  "type": "keyword",
                  "ignore_above": 256
                }
              }
            }
          }
        },
        "ecs": {
          "properties": {
            "version": {
              "type": "text",
              "norms": false,
              "fields": {
                "keyword": {
                  "type": "keyword",
                  "ignore_above": 256
                }
              }
            }
          }
        },
        "geoip": {
          "dynamic": "true",
          "properties": {
            "ip": {
              "type": "ip"
            },
            "latitude": {
              "type": "half_float"
            },
            "location": {
              "type": "geo_point"
            },
            "longitude": {
              "type": "half_float"
            }
          }
        },
        "input": {
          "properties": {
            "type": {
              "type": "text",
              "norms": false,
              "fields": {
                "keyword": {
                  "type": "keyword",
                  "ignore_above": 256
                }
              }
            }
          }
        },
        "log": {
          "properties": {
            "file": {
              "properties": {
                "path": {
                  "type": "text",
                  "norms": false,
                  "fields": {
                    "keyword": {
                      "type": "keyword",
                      "ignore_above": 256
                    }
                  }
                }
              }
            },
            "flags": {
              "type": "text",
              "norms": false,
              "fields": {
                "keyword": {
                  "type": "keyword",
                  "ignore_above": 256
                }
              }
            },
            "offset": {
              "type": "long"
            }
          }
        },
        "loglevel": {
          "type": "text",
          "norms": false,
          "fields": {
            "keyword": {
              "type": "keyword",
              "ignore_above": 256
            }
          }
        },
        "message": {
          "type": "text",
          "norms": false
        },
        "thread": {
          "type": "text",
          "norms": false,
          "fields": {
            "keyword": {
              "type": "keyword",
              "ignore_above": 256
            }
          }
        }
      }
    }
  }
}