Are you using the Somfy Sun sensor?
I use the Tahoma bridge and the Homey Tahoma app which gets the light data from the Sunis iO sensor to control all my curtains and blinds.
If you are using the Homey Somfy RTS app then you will need a non-RTS / iO sensor as Homey can only send RTS commands, so can’t read those sensors. In which case you could use a light sensor connected via z-wave / Zigbee or WiFi.
All these solutions would require one or more flows to do the automation.
Edit: I’ve not come across the Auto state so can’t help at all there.
