Rising temperatures erode human sleep globally
This comment won't do well right now but I suspect in the future we may come back to this idea.  I believe more work needs to go into automation of forming/welding frames for underground homes as the temperature is rather constant under ground. 3D printed/molded?  Some locations will need specially built units that can handle moisture.  I have probably binge-watched too many mining/tunneling videos but I could see this technology becoming affordable to the consumer through technological optimizations, maybe?  Anyway moving the home under ground could provide additional room above ground for a garden or parking spots.  Underground homes would also be tornado resistant.  Another advantage is energy efficiency or moving towards being carbon neutral.  There are concrete / shotcrete companies making carbon absorbing material now.I am thinking of the real world example of Coober Pedy, AU [1]  They have subterranea hotels, mines, homes, recreation facilities and more.  If I ever went to AU that would be my first stop.Anecdotally my home is partially earth bermed and even on hot days hot being around 101F it is cool in my home and I do not even own a HVAC unit.  One of the many reasons I moved was due to heat and sleep issues.[1] - https://en.wikipedia.org/wiki/Coober_Pedy