Geothermal should be an obvious choice for new-build homes. Put a ground-source heat pump source in the ground, and build your home on top of it.
Residential geothermal for home heating and cooling could make a ton of sense, but more likely based on the scale of a residential natural gas network.
Drilling a hole per home is super expensive. Replacing gas pipes with moderate thermal pipes would be about the same cost as gas infrastructure but allow the massive efficiency gains of larger scale. Heat pumps operating on pumped water through these sorts of pipes doesn't need very high or low delivered temperatures to be effective, as long as it's somewhat above the -20C of the extremes of winter.
Thermal storage quantity scales roughly with volume (x^3) and storage costs roughly scale with surface area (x^2). Though I'm not sure if storage plays much into the gas -> thermal plans that have been explored.
They currently are efficient but still expensive because of a law that the pricing has to be similar to heating with would have been.
The city heating network operator is a monopoly, that is why the price is capped.
Even though city heating networks utilize 'waste heat', the capital cost of the network is significant. The price cap and the capital costs (especially now with higher interest rates) led to many proposed projects being cancelled in recent years.
If you live in a place like Minnesota, then the ground-source pump needs a water table. Or you'll just be freezing the water in the ground. And you'll likely still be better off with an air-source pump.
(note, the 6 to 8 feet is for a closed loop, horizontal system)
It looks like this: one day in winter, the temperature of the coolant in the loop outlet falls below 0C. And after that, it starts dropping down by about 1C a day, until the pump becomes a resistive heater. If you sized your loop correctly, it hopefully happens towards the end of the heating season.
I don't have a personal experience with vertical loops.