Geothermal works in enough areas (geographies) for it to be an entertaining talking point in niche forums like this one.

But not much else.

Earth is an incredibly poor heat conductor, as evidenced by the fact that you don’t have to dig very far, maybe a foot or four, and it’s a fairly constant 14 degrees C, and yet the core is molten lava (rock) and has been that way for billions of years predominantly from latent heat from the planets formation.

So you have to be very careful with heat exchange, lest you exceed the ability of the earth to conduct heat through the rock surrounding the boreholes.

Drilling deep boreholes is difficult as the rock becomes more like plasticine as it approaches temperatures where usefully higher temperatures occur.