If you can get yourself to Thailand and dont have an aversion to Buddhism there are Buddhist temples where you can go stay. Frequently you make a donation at the end of your stay with the amount being at your discretion.
Also look into Christian monasteries near you. I'm not Christian but spent a silent weekend at a Cistercian monastery and it was amazing. They suggest a donation but there's no charge. Only have to schedule a month or two in advance.
I suspect that people are looking for something more structured. For that matter, just go on a backpack someplace that doesn't have cellphone service (or just leave your cellphone in the car).
I'm not sure what your point is, but I certainly wouldn't compare airbnb to "random street trash". The quality does vary, but if you're careful you can get amazing places.
The Vipassana silent courses put on by dhamma.org are entirely free, run by volunteers. The popular locations are fully booked months in advance, but if you have a very flexible schedule you can get on the waitlist and be accepted right before the course, that is how I did my first one.
I've done two 10-day courses from them. After my first one I described it to people as like being in prison, never having gone to prison, but with less freedom than prison. But I still went back for a second time :)
Goenka’s 10-day vipassana retreats are not only free, but (at least when I took it) they would not even accept donations from those who hadn’t yet experienced the course: https://www.dhamma.org/
An example near Chiang Mai in north west Thailand https://www.fivethousandyears.org/