Underground construction generally isn’t cost effective. It costs way more to get dirt and rock out of the way than just building a frame upwards. There might be other reasons to do it, but you want to avoid it if possible.
The underground suggestion was only to counter the argument of space usage.
There’s a million other ways to go. Solar on every parking lot, over every irrigation canal, and along every highway. Some farming can be done under solar panels, as well; some commercial crops prefer shade, such as strawberries.
The US uses about 30% of its land for cows. One simple plan is that we all eat one less burger a week. Which would be a good idea, anyway.
Land usage is so not a problem as soon as you open up the dual use possibilities.
For dual use, I’m particularly partial to the solar fence
