It's harder to sanitize underground. The sun does it for us on the surface. You'd have to keep an army of UV emitting robots crawling everywhere, all the time.

You also need forced ventilation underground. You can certainly ban fossil fuel burning, and really almost all combustion. You can't prevent combustion through accidents. In the right conditions, even a 'small' underground fire could kill hundreds, even thousands.

Earthquakes. Big problem. You can't get 'outside' from underground. Tunnels and structures will collapse, with nowhere to run to.

Aquifers. Underground is wet. How wet? Well, according to the depth of the local water table, anything you build underground will completely fill with water, without active pumping. During an earthquake, seals and structures and machinery designed to prevent flooding can (and will) fail. Imagine what happens to an ant hill in a flood.

These are all planning and technology issues.

I would recommend glass domed, protected cities. Translucent glass can be built thick as bricks, to allow daylight into the city. Even keep the top open most of the time, to freely exchange air when there are no problems. Sand can be stacked on the dome to a protective depth, and parks and gardens and farms can be built on it.

It's not perfect protection, but it will prevent anything but a direct hit from wrecking things. A direct hit on an underground city would be just as big a disaster, only there's an unforgiving amount of mass on top of it.

Any way you slice it, you have to choose the geology upon which you are building very carefully.

The 'safest' plan is for the city to be self-sufficient enough to last a few years of isolation. You know, let the 'mad max' clowns kill each other off before you go out and seek resources and trade.

More important, self-sufficiency means that a city-state of this nature would be resistant to economic downturns. If you all produce everything for yourselves locally and sustainably, you're not going to be unemployed because some bullshit happened in China.

Besides, it's all good practice for space colonization. A Mars colony won't be able to just have cheap Asian goods and American food shipped to it on cargo ships a million tons at a time.