You are right, i must setup passcode for the device itself, the problem i dont think it’s convenient to put a pin code for a device attached on the wall inside your private room and this device meant to be used instantly to switch on/off your lights
Just try if you can remove the code of the device after you enable kiosk-mode. You will need to setup a code to exit kiosk-mode later. I do this on my Android-tablet.
I also use Fully kiosk to have the app running in kiosk-mode. Don’t now if Fully kiosk supports your devices.