Sorry to hear your struggling. I have four separate weather measuring type setups. Nothing sending to the cloud though, I haven’t had that need so far. I just like to know what the current conditions are, right here right now type of thing. I do have one setup that graphs the temperature, humidity and pressure so I can see trends, but its not logged to a file. It’s just displayed in a graph on the LCD.
I do agree with your privacy concerns. I struggled for a while to find a Pi camera setup that would let me watch the camera video stream without having to stream it to the internet first. I just wanted to view it on a PC over my LAN. Luckily Motion Eye OS will let me do that.
There are a few here doing the mqtt thing to a local PC. Not sure about HomeKit though?
Found this via search, might be worth a look see?
Enviro+Air Mqtt-all.py - connects to broker, but data is not shown in HomeAssistant - Support - Pimoroni Buccaneers