I got the enbrighten switches set up on the bathroom fan. After a few months of observing the humidity changes I settled on triggering the fan based on the derivative of the humidity. I found that 2%/s with 2min of averaging works well, no false positives so far.

what relays do you recommend?

I’m think about putting them on bathroom fans as well. It would be really nice to have them automatically turn on/off based on humidity.

I was looking at the Enbrighten switches, the zigbee ones are on Amazon but they only list them the z-wave ones the Enbrighten website. Maybe the zigbee ones were discontinued? Seems like the industry is moving toward z-wave, maybe I should get a z-wave adapter as well.