Is Orbi compatible with Vivint home security

I agree with Vivint that replacing the AT&T WiFi with Orbi WiFi is not likely to cause any problems for Vivint. The key is (1) to disable the AT&T WiFi so that its radios do not compete with the Orbi radios, and (2) to install the Orbi in Access Point (AP) mode so that the AT&T system remains the "router".  I would also set up the Orbi with exactly the same WiFi name (SSID) and password as the current AT&T.   This way, every device that currently connects to the AT&T will connect to the Orbi using the same credentials.

I was unable to find many technical details about Vivint.  My security system originally came with only a cell phone connection.  i.e. it could connect to the monitoring service even if power is out or my phone line is cut.  It was upgraded to offer a WiFi connection in addition to the cell phone connection.  So, as long as WiFi is working correctly, things happen almost instantly.  If the WiFi goes out, the cell phone connection is pretty fast, but not as fast.