In past 2 weeks, in our whole neighborhood, Comcast had at least 10 outages. With the Universal Devices (Polisy-Eisy) I get a notification when it is disconnected and when it is connected again. Can I set up the same with HA (using Nabu) ?
Comcast is obviously the wrong choice for TV and Internet, but unfortunately living in a condo I can ot choose my own provider, but if you have a choice, stay away from them.
The DNS IP integration…
…gives you a sensor sensor.myip which will tell you when the internet becomes unavailable. By definition, though, you won’t be able to send a notification. 
You could try using another device with its own internet connection - a mobile phone, for example. An app like Llamalab Automate could ping Google every few minutes and send a text if there’s no response.
Thanks. In principle I understand your “by definition”, but as I mentioned it works with the Universal Devices hub and theoretically it should be possible for the Nabu service to send a notification.
Thinking about it…
Documentation is a bit thin on the ground, but as far as I can see Nabu Casa is not a cloud server in the normal sense - it doesn’t store data or run applications. Your server is your Raspberry PI (or whatever). Nabu Casa’s function is simply to provide secure connectivity on demand. I’m not sure they have any way of telling whether you have an internet outage.
I personally have gone the Llamalab route - one of my wall tablets happens to have a SIM slot, so it pings periodically and sends me a SMS if there’s no connection. It does this independently of HA.
Have you thought of getting a router with LTE backup? I use mobile broadband all the time and it’s getting better and better as providers upgrade their networks. You need a good signal, of course.
I had never heard of routers with LTE backup and I will look into that. Thanks