> If I could find a reputable construction company to build my underground home I would be a true troglodyte

If you have the resources you could always buy an existing underground structure and renovate. Like a missile silo. Or buy an already renovated one:

https://washingtonmissilebase.com/

I imagine upkeep is pretty expensive, probably needs a lot of HVAC, dehumidifying, pumping, etc to keep you from dying due to weird mold and stuff lol

I looked at many of those. Plenty of people are indeed upgrading silos. I looked at the cost to repair and overhaul these facilities but it would be just a little more to do it right on my property with high performance high pressure concrete and do it right in a place outside of the nuclear sponge. Only challenge is getting the right people up here but I will not give up on the idea.