Fired it up again, manely as a humidifier for exceptionally dry air rather than to cool the room.  2021 onward were characterized by persistent offshore flows.  The marine layer of the historic climate is all but gone.  

A very expensive indoor hydrometer was built to know when it was safe to print TPU & to know what effect the swamp cooler has on the air.  The AHT20 board is a waste of money.  There are fully assembled hydrometers for a lot less money which can be scavenged for parts.  The mane desire was a larger display.

The swamp cooler ended up adding 5% when there's no ventilation.  When the room is ventilated, it doesn't add any significant amount of water.  It has a surprisingly limited ability to hydrate the air.  The biggest effect on humidity comes from taking a shower.  That adds 3% despite the bathroom having an exhaust fan.

There's still a desire to improve the airflow around it by making it smaller & make it waste less water.  The transducers can be closer together.  The front lid can be a single piece.  Wires should go straight up & have a hot glue channel instead of scotch.  The bottom of the water tank can be higher than the screws & diagonal.  The bottom corners don't have to be square.  The water sensor still needs a gap.