I’m a fan of the Airthings products for Radon. I’ve had an Airthings WavePlus for years with an Airthings Hub. Solid units. I’d imagine the Airthings View Plus would do the same these days. I bought an Airthings WavePlus, then I learned my high radon levels and bought a radon mitigation system for my house. I live in CO where we have high radon levels.
When you don’t need Radon and want an easy solution, the IQAir Airvisual Indoor and Outdoor units are great and supported by smart people on HA. I have not looked recently for the outdoor unit support but I have been able to view all the data for my indoor unit and the AQI on my outdoor unit (it sync’s with the indoor unit) for a while now. Again, solid devices that are easy to get into HA.
I want to add monitoring to more rooms in the house and now looking into other options. Will report back if I find something less expensive than the above that are as easy to integrate into HA.
Holler if you have any questions.