When upgrading this device requires AHT2x support which is not included in default tasmota builds and requires a custom binary.
Add Humidity Level Rule:
rule1 ON AHT2X#Humidity>80 DO power 1 ENDON ON AHT2X#Humidity<75 DO power 0 ENDON rule1 5 rule1 1
The numbers 80 and 75 in the command are humidity valoues of when you want to turn on and off the fan. It means the switch will turn on when humidity is over 80%, and turn off when it goes down to 75%.