For those curious, for all of history, mankind has probably only dug a few dozen or so holes a mile deep or deeper. It’s not easy
That is not really what the article is discussing though. They are talking about putting it down a drilled hole, and a mile is a very common depth for drilling. In a USGS publication summarizing deep wells in the US through 1998 [1], it talks about a dataset of more than 20,000 wells over 15,000ft (4,572 m), more than 1,000 wells over 20,000ft (6,096 m), and 52 over 25,000ft (7,620 m).
Obviously, that’s not a meter wide hole, but it’s clearly possible.
https://www.researchgate.net/figure/The-average-temperature-...
> The average temperature gradient for planet Earth is 20 °C per kilometre. In many areas around the world the gradient is higher, and the temperature increases at a faster rate with depth below the ground. With a temperature gradient of between 50 and 100 °C geothermal resources are more readily accessible. Above 20 °C geothermal waters can be used for direct uses like greenhouses, aquaculture and district heating applying heat pumps. Above 75 °C the water is hot enough to be used for electricity generation using binary cycle technology. Above 160 °C flash steam generation can be used to produce clean, renewable electricity. Source: Geothermal Resources Council