Do you have node exporter running on the pi?
Prometheus node exporter on Raspberry Pi - How to install - Linuxhit
Node exporter is a great way to monitor your Raspberry Pi with Prometheus. Follow these steps to get node exporter running on your Raspberry Pi.
linuxhit.com
. Its bit complex, but its as (if not more than paid solutions) advance and powerful mertics/telemetry stack as you can get (through FOSS)."

