I've got my ISY setup on my home LAN, which doesn't have external access enabled (except via a VPN that I use when I travel).  Every time i launch the Admin Console I get this Security Warning alert.  Neither button seems to do anything meaningful, other than dismiss the alert.  How can I get this alert to stop showing up?  I'm happy to install a LetsEncrypt certificate if needed, or something like that.  

Same here. 

Well, I don't know why I didn't see this before, but I just found this old thread:  

In there, Michael mentioned simply using a self-signed cert, with a link to the details in  http://www.universal-devices.com/docs/I ... 0Guide.pdf. I just did that and that seems to have done the trick.  Just took a couple clicks using the dashboard and not the admin console, which was where I had been looking.  

I have found better performance offloading the SSL encryption to Stunnel on a PC.  If you find slow connections to the ISY using HTTPS, consider this option.