Senseair S8 paired with ESP-32 has served me well over the past 3 years, but they have to be exposed to outside air at least once a week or so. Otherwise they quickly lose their zero point and start reporting thousands of PPM as mere hundreds.

I think other models with auto-recalibration also suffer from this (including MH-Z19). It's probably not a problem for you, but if you too live in an extremely polluted area and have to keep your windows shut for weeks at a time, it might be.

I got the Netatmo Smart Indoor Air Quality Monitors. They are somewhat expensive, but I got a good deal, 69 EUR a piece. They also monitor temperature, air humidity and noise levels.

Airthings, expensive but just does the job perfectly.

I’m quite happy with Qingping Lite. Doubles as a clock, PM10, charges via USB-C.