Extending core metrics with Raspberry Pi integration

I’m using the Raspberry Pi integration with Grafana Alloy and I would like to extend the built-in metrics being captured for my more customized setup. Is there a guide or good way of doing this? I’m interested in capturing more “OS level” data (e.g. LTE RSSI for a modem I have connected) as opposed to custom service/app data.

Thanks!
Bryan