If I remember correctly, continuously extracting a few gigawatts of heat out of the volcano would be enough to stabilize the Yellowstone area.

https://www.bbc.com/future/article/20170817-nasas-ambitious-...

This might be the report that the coverage refers to: https://scienceandtechnology.jpl.nasa.gov/sites/default/file...

What about the one under Naples which given the immediate population centers would seem more urgent to diffuse and defuse.

I had exactly this thought recently when relatives watched a documentary about volcanoes!

The same tech could be used, more or less, on pretty much any volcano.

Sure! Iceland for example has so much geothermal energy that they can clear their sidewalks from snow by heating them. Amazing, isn't it? (Searching for "iceland heated sidewalk" should bring up enough results if you are interested)

I'm thinking it may be a good idea to tap those thermal sources' energy to make ice to replenish melting glaciers.

We can, although I don't know how effective it is to do so from a volcano. https://en.m.wikipedia.org/wiki/Thermoelectric_effect

Those things are extremely inefficient. Here is how it is done.

https://en.m.wikipedia.org/wiki/Geothermal_power