I think this is a test that everyone should who has a smart home should do at some point. It really isn't possible to know what does or does not work in your smart home until you actually unplug it from the outside world. We have seen too many times situations in which a cloud-based smart home provider disappears, leaving their customers high and dry.
I did this exercise for my smart home because I was curious about what would happen. I've tried to keep as much local control of devices as I could but I'd never really tested it.
I will be looking at my Home Assistant Dashboard as well as an internal monitoring tool to monitor the status after unplugging.
You'll have to watch the video for play-by-play, but I can say that I wasn't surprised by most of what I saw, but there were a couple of devices that I was surprised about.
The cloud-based services obviously stopped working (became unavailable).
What was surprising was that one of my local access points, along with the cameras behind it, started having latency issues.
I'm going to have to spend some time figuring that one out because it shouldn't do that and I'm not sure why it's happening.
The other surprising thing was the Roku. In the past, losing the Internet would mean that it would not see a network connection and not function at all. This time, it was able to stream my local plex stored media. However, live channels did not work, likely because the Plex Pass required for that couldn't be verified.
At least now Roku gives you the choice of proceeding or not. This did not use to be the case.
You can see all the details and discussion in the video below. Please take a moment to watch, and if you are not a subscriber of my YT channel, consider subscribing. Thanks for reading and watching!