I think I might like having a Tiny House (probably not underground) :

[en.wikipedia.org]

I have become a fan of the tiny home movement. It fascinates me how one can have a comfortable lifestyle in a small, well-thoughtout space. If I were in such a position I would definitely go for a tiny home. Some close friends live a similar life. They have a wood yurt which is a warm, comfortable space. The heat with wood only and their kitchen is outside and it is used all year round. There is an outhouse (composting system) and their shower uses rainwater which has to be heated with a wood stove. They choose to live this way BUT, as with many of us they are getting older and looking for a few more 'creature' comforts. This is one extreme that most of us envy but could not adopt. There is a great, older film by PBS about a retire living in Alaska that choose this lifestyle on an even more extreme. It was a very popular series and can be found in entirety. Here is a trailer.

This is unique, it is respectable and I don't want to undermine his efforts. If it is working for him, I am happy for him.

But I like modern living with amenities of warm water, a comfortable bed, small but a cozy, comfortable home, the internet and medical care nearly if needed. I have loved it more after being miserable with no good home, enough food, clothing amenities (gas shortage, electrical shutdowns - load shedding), lousy infrastructure, bad transportation in my early to young years. I hated it every day.

That is the thing. I have observed that in Western societies, we have a fascination for being near the nature, jungle living, kayaking to remote places, carrying your waste to dump centers, remote living, cave living and so on. Ask people who are struggling with daily lives without amenities, their dream is just want have a comfortable life, just 'basic' comfortable life is their dream. I have never heard, seen or read about people wanting to live in caves, live in remote places, being a minimalist etc. in 3rd world countries. This is a phenomenon in the comfortable Western societies. We are always attracted to seeking what we don't have.

However, financial minimalism and reducing your needs have appealed to me. I have been after financial independence for a year after insanely spending money on me, family, entertainment, clothing, buying things and so on. My home looks like a museum with things I bought on overseas trips. Now, I am on financial minimalism and my targets of increasing passive income, high savings and more free time are within reach. That is my approach.

I would never do what this guy is doing. What is simple and happy to him is miserable to me.