IIRC, the recommended way to integrate it with Grafana is via promtail but we weren't too keen on the added complexity of yet-another service in the middle so we developed a custom client library in Go to just send the logs straight to Loki (which we should probably open source at some point).
I don't think there's any fancy graph integration yet, but the Grafana explore tab with log level/severity and label filtering works well enough esp. since they introduced support for pretty printed JSON log payloads.