I have a PM2.5 sensor hooked to a Raspberry Pi Zero W, I use the PMS5003 ($40 at Adafruit). I have a script running in a screen session that posts its measurements once a minute to a Google Cloud Function which then inserts it into BigQuery, and then a DataStudio dashboard to visualize the data.

The cloud cost is $0, it all falls in the free tier. The Raspberry Pi Zero W is just $10.

I have a separate station with an SCD-41 CO2 sensor (+ temp/humidity/pressure with an MCP9808) all hooked up to a TinyPico board with Stemma QT that also post metrics to BigQuery in a similar way. And yes I'm planning to combine both into a single device very soon :-)

So currently I'm not using any. (the list above is what I am NOT doing)

Previously, I had sensor from this family hooked up to a Raspberry pi doing measurement only:

https://www.amazon.com/AITRIP-Precision-Quality-Detection-Co...

Oh, ha! So much for my reading comprehension. Thanks for the link. I think that should be compatible with a Pi. I can try it out in a couple weeks when I get some free time to tinker.