@Rich1000 

Most home control solutions out there are 'cloud' based, meaning your light switch is connected to the cloud and so is your phone.  I have automation devices from at least 4 different vendors and ALL of them use the cloud...there is no direct connect between your phone and your light switch.

The reason they do this is so you can access your stuff remotely, ie turn on the lights before you get home, pre-warm the hot tub, etc.  It's also exactly how the OC200 works when you 'cloud connect' it.  The Omada app even has different tabs for 'Cloud' access and 'Direct' access of your sites.

So when your ISP goes down, even if your phone can access the internet via LTE or whatever, your lights witch can't.  Now, if you hotspot your phone and you have a wifi-ethernet bridge attached to WAN2 and connected to that hotspot...you could turn off the lights without getting off the sofa.  You could also ring up a pretty wild data usage bill too.

  @Rich1000 

You are correct about the printer, because your printer IS directly accessed via the local network.  However, the home automation devices (if you were to look at their actual network connections) you would see that they have connection(s) only to servers on the internet and never directly to your phone or other local LAN devices.  So when you break the the loop to the internet and back, you break the connection between your phone's app and your light control device.

If you want survivable control, you need to use a different technology like Zigbee devices that DO work only locally, and usually via a gateway controller which you must also buy.