services.grafana.declarativePlugins

If non-null, then a list of packages containing Grafana plugins to install. If set, plugins cannot be manually installed.

Keep in mind that this turns off drilldown: for this to work, you need to add grafana-metricsdrilldown-app, grafana-lokiexplore-app, grafana-exploretraces-app and grafana-pyroscope-app to this option.