Sorry for the delay. This is what I get when I set the HA thermostat cool. It sends that command to the Pearl thermostat just fine.
2022-05-10 17:23:14 DEBUG (MainThread) [pydeconz.gateway] Sending "put" "{'mode': 'cool'}" to "http://core-deconz:40850/api/B513B2AC31/sensors/113/config"
2022-05-10 17:23:14 DEBUG (MainThread) [pydeconz.gateway] HTTP request response: [{'success': {'/sensors/113/config/mode': 'cool'}}]
2022-05-10 17:23:14 DEBUG (MainThread) [pydeconz.websocket] {"config":{"battery":1,"coolsetpoint":1800,"fanmode":null,"heatsetpoint":2000,"locked":false,"mode":"cool","offset":0,"on":true,"reachable":true},"e":"changed","id":"113","r":"sensors","t":"event","uniqueid":"00:0d:6f:00:05:78:15:a6-01-0201"}
2022-05-10 17:23:16 DEBUG (MainThread) [pydeconz.websocket] {"e":"changed","id":"113","r":"sensors","state":{"lastupdated":"2022-05-10T05:23:16.082","on":false,"temperature":2144},"t":"event","uniqueid":"00:0d:6f:00:05:78:15:a6-01-0201"}
But when I set modes on the Pearl, nothing seems to appear in the logs.
However, adjusting the setpoint on the Pearl does results in logs and subsequent action in HA. However, I see from the logs that the mode is stated as cool and it was not. I set it to Heat and then 28 degrees so the temp is being sent correctly but the mode is not.
2022-05-10 17:28:47 WARNING (MainThread) [homeassistant.components.sensor] Updating snmp sensor took longer than the scheduled update interval 0:00:10
2022-05-10 17:28:54 DEBUG (MainThread) [pydeconz.websocket] {"config":{"battery":1,"coolsetpoint":1800,"fanmode":null,"heatsetpoint":2800,"locked":false,"mode":"cool","offset":0,"on":true,"reachable":true},"e":"changed","id":"113","r":"sensors","t":"event","uniqueid":"00:0d:6f:00:05:78:15:a6-01-0201"}
2022-05-10 17:28:54 DEBUG (MainThread) [pydeconz.websocket] {"e":"changed","id":"113","r":"sensors","state":{"lastupdated":"2022-05-10T05:28:54.101","on":true,"temperature":2168},"t":"event","uniqueid":"00:0d:6f:00:05:78:15:a6-01-0201"}