Off line back up

Nabs3000

I understand homey works  from the cloud. How about an offline back up should the external network go down?

bvdbos

Homey doesn't work through the cloud, it works locally:
https://www.athom.com/en/support/KB000028/

Offline Homey will still be able to manage your home, as Homey is not dependent on cloud services to operate (unlike some other systems). Functionality that remains available offline includes:

• Controlling your home with the Homey Smartphone App while you're on the same WiFi network
• Executing flows that don't need internet, for example sensor based ones
• Voice output, allowing Homey to speak (for example in flows)
• Logging of your local sensor data in the Insights module

Conclusion

In short, all the capabilities that do not clearly require internet work.