I've had my ISY for ~5 years, and mostly happy... apologies for this basic question.  Is my system "stand alone" or does it require a Universal Devices server somewhere?  I was thinking the Admn Console was software I installed... but maybe not?

The ISY is generally standalone and core functionality requires no internet connection - with a couple exceptions.  If you use email, you might be using UD servers (or you can use any other email server).  If you use the UD portal, for things like Google, Alexa/Amazon, or IFTTT, you would be using Universal Devices servers.

But, the core functionality of controlling Insteon or Zwave devices does not require the Universal Devices servers.

 

Was there a reason for your question?

in addition to what @Screw Loose Dan mentions....   The Launcher uses the internet and a UDI server to open the admin console.   The purpose is so that you always open the correct version that matches your firmware version of the admin console.   The Launcher is not required tho, you can use other means to open the correct version without that dependency... uses the launcher is just easier for most people.

 

Should, for some reason, the UDI server be down, will the launch work to start the admin console? And if not, what is the "plan B" eluded to above?

 

You should be able to always download the admin console from http://your.isy.IP.address/admin..jnlp and run it.