How to integrate a scientific RPi "Cluster" into HA?

Hi *,

I finally have my solar panel online with a MPPT controller connected via Modbus.
To use the solar power more efficiently during daytime, I need configurable load.

Today I came up with the idea of a Raspberry Pi “cluster” (I have 8 old 1A Pis lying in the drawer) that is doing BOINC calculations.
Depending on the energy that the solar panels provide, HA shall start the RPis one by one. and shut them down at dawn. I also want to monitor some aspects like CPU load and maybe some BOINC statistics.

My question is now how I would realize this with HA.
My first reflex was the same as always: MQTT.

But I wanted to ask if there are other means that may be more elegant?