As my knowledge you don't need to configure PrometheusMeterRegistry if you are using spring boot 3.x. You just need dependencies for metrics which you already have.

Make sure that you have enabled exemplars in prometheus https://prometheus.io/docs/prometheus/latest/feature_flags/#exemplars-storage

And in the promql in grafana you will have toggle to enable exemplars for specific query.

Finally make sure that you have configured connections in Grafana: Home -> Connections -> Data Sources -> Prometheus/Tempo/Loki (If you cannot edit connections, then you need to make it editable in grafana deploy configs).