I went with the Levoit 200s (have not tried to flash as I am not sure if the one I have can be) since I did not have the budget at the time for the 300s that was suggested which has been great so far but if you have the budget get that 300s or 400s for the ability to reflash it to be local only:
Others may suggest something more out of the box for you they have experience with.
I have an automation to set the fan mode to silent on it when its turned on either manually, through my bed sensor when in bed or have it automatically turn on when the Air Quality Index for my area is above 50 and it lets me track the filter life directly in HA so I know when its time to replace it:
