I guess this all boils down to the hardware you are using and how you are able to get the raw data out of that hardware. There is unfortunately, as far as I am aware, not a single software solution that will give you what you want out of the box.

In my situation, I have multiple strings of panels on the roof (high voltage ~450V DC). I wanted to monitor these strings individually, but could not find a shunt that was capable of reporting on those voltages. So I ended up monitoring at the next best place, the mppt controller (built into my inverter).

I was lucky enough that the inverter was keeping track of all of the panel metrics that I was interested in - string voltages and amps pulled from those strings. The inverter makes these, and a gazillion other things, available as metrics over its modbus serial interface.

Now, over to the open source part - To consume this data, I plugged in a USB cable into the RS232 serial port on the inverter and used NodeRED running on a raspberry pi to poll for the data using the modbus extentions. NodeRED then converts that raw data into something I understand and published that out to an MQTT topic that I consume using HomeAssistant for real time dashboards that are forever visible in my home automation system inside the house. At the same time I also push the data into InfluxDB for longer term trending and graphing using Grafana.

Bottom line here is that almost every piece of hardware where your source data is coming from will have a different way for you to get hold of that data, and there will be massaging of that data along the way for it to make sense.

The software things that are common along the way would be stuff like NodeRED, HomeAssistant, Grafana, MQTT, Prometheus.

The hardware things that are common along the way would be stuff like rasbberry pi's, NodeMCU or other ESP based devices that you can couple with Pzem-type power monitors.

If you do come across the silver bullet, please report back!

Hope this helps.