Yes, full manageable thru the Web App, but only using grasshoppers?
beside that the Homey uses a Let’s Encrypt Certificate for *.homey.homeylocal.com.
These certificates have a lifetime of 90 days. I expect it can switch a mobile App to un-encrypted but for normal operation Homey self needs internet to renew these and also because it doesn’t have a RTC and time probably will drift soon or after powercycles.