How to scrape metrics from bitnami/mariadb helm deployment with kube-prometheus-stack

Question

I am using bitnami/mariadb helm chart deployments. I tried to enable the metrics and servicemonitor like below in the primary and secondary section in values.yaml file. And I noticed that the sidecar container and servicemonitor are not creating.

    metrics:
      enabled: true
      image:
        registry: docker.io
        repository: bitnami/mysqld-exporter
        tag: 0.14.0-debian-11-r37
      annotations:
        prometheus.io/scrape: 'true'
        prometheus.io/port: '9104'
      serviceMonitor:
        enabled: true
        interval: 30s
        selector:
          release: prometheus

I have enabled the metrics in other bitnami apps like above. But I am not sure why it is not working here.

K8s version: 1.21
MariaDB app version: 10.5.11-debian-10-r25