They've got drawbacks, too, especially since most examples of them in residential construction are the efforts of, shall we say, enthusiastic amateurs.

1. Because soil holds moisture for an extended period of time, they tend to get saturated, and then excess moisture migrates down to the waterproofing system, which will inevitably leak over time. Most amateur-built earth sheltered homes are not using particularly sophisticated waterproofing materials, and rarely take a defense-in-depth approach to them that could mitigate a failure in one layer of the system.
2. Maintenance is expensive: once any part of the waterproofing fails you are going to have to dig it up to repair it.
3. Soil - especially wet soil - is heavy and the prescriptive structural parts of residential building code aren't really intended to address this kind of construction. You need an engineer to ensure the house is properly structured for the loads involved, and if you're building new that extra structure is going to cost money and limit design options.
4. Building into a slope to allow roof access for planting, mowing, etc., limits daylighting options, and particularly in the US where bedrooms are required to have an egress window it can be nearly impossible to design a floorplan with the expected gradient of public to private space.

Don't get me wrong, I love the concept, and I've even drawn up plans for one I'd like to build on the lot next door to me once the nigh-derelict rental house currently occupying the space gets condemned... But this is one case where I absolutely do not want to be buying somebody else's project. I don't trust the other people who build them to do it right.

5. Camouflage your bunker from airstrikes and air reconnaissance.

The only fault? Dude shoulda made it look like a hobbit hole, it wouldn’t have stayed up a day on the market.

I don't know. I looked at the photos, and I'm pretty sure this place is built for drugs.

I can see the value in that, basically nature's insulation - though I'm not an architect nor an engineer, but that looks like a flat roof - so would overgrown grass or sodden soil put some crazy weight and pressure on the structure?

The point of this place looks more like it's for building bombs without having the government find you.

but passed during construction having spent over $400K on the project.

A boomer building a bunker.

Thank you I will ensure to do so

FYI, that's called the query parameters. They're usually used for tracking, but also could be used for non SEO optimized links to tell the site what item or article or such you're linking to.

Most sites are SEO optimized, and their URL is the human readable description. But not all sites are like that. That's why some break when you remove the query parameters.

It was definitely a boomers bunker. A capitalist stronghold being usurped by the Solarpunks is short-story worthy.

Zero percent chance any of it, at the very least the septic, could be permitted after the fact. It is nice Bo is at least disclosing it has an unpermitted on-site septic system, but a bootleg OSS is more expensive than no OSS at all.

Source: used to work for the county where this site is located.

It's a house for elves. Don't you think?

5 acres for 245K between Seattle and Portland is nothing to sneeze at

This isn't that far from the Ramtha School of Enlightenment cult and when we were trying (and failing) to buy a home in the area we toured two similar places with bomb shelters. They have mild doomsday lizard people teachings.

the underground design means that rooms in the back will get no natural light, which would be pretty miserable.

Much like a basement in a regular house.

How bad it would be for air quality and exchange would come down to the HVAC almost entirely as long as the build quality is there. A modern energy efficient house is sealed so tight that the sum of all air leaks to the outside is smaller than a baseball.

The build quality would of course be the biggest concern, if they didn't do the weatherproofing and water management right there would be water seepage and a high likelihood of a roof leak that would be horrendous to address.