I've heard about Scottish bothies. As an American, culturally it seems hard to imagine not only a right to walk over private land, but land owners sometimes even donating shelter for use by strangers, for free.

Bothies are awesome:

https://www.mountainbothies.org.uk/

My favourite is probably Camasunary:

https://annestravelsandhikes.com/2018/02/16/a-walk-to-camasu...