I still have problems with this, and for the most ridiculous reason.
When my internet fails (rural, crap service) I fail to be able to control my devices. Not because Hubitat fails - it does not - but because my mobile phones "helpfully" realise they have no internet access and disconnect themselves from the WiFi. No dashboards, or other interactive control.
All the motion sensors, buttons and routines work perfectly, but modern "smart" phones are annoying.
I need to work out how to create a wall pad or something with fixed access to the dashboards regardless of whether the internet is working. Just another job...
I am not aware of any modern cell phone that would lose connection to the internet and would stop having local access to network resources. I do this all the time when re-purposing older Android cell phones. I create firewall rules that prevent internet access but they can be used for dashboards, voice announcements, etc. I even setup one to be a Tier 1 time server and it didn't need any internet access to service time requests to the network. In the android message area they show no internet but they are still connected to wifi and talk to devices on the network.