I finally set up HomeAssistant on one of my PIs and wow, I wish I did this earlier.
Pi #3 is the one running HomeAssistant and installing was super easy, just followed their instructions to flash the SD card and it's ready.
I already had a few Matter devices and I was able to load them into here. I bought a few more of the IKEA devices and they worked really well.
The data from the IKEA devices just loads right onto home assistant. Now I have actual proof that my room is boiling hot.
The next thing I want to setup is something that gets my electrical usage across the whole house so I can better display that. If we ever get solar, this will be very handy to see how much capacity we'd need to not be reliant on the grid.