I’m very interested in hearing the answers. Many things about libertarianism appeal to me in some ways, but I don’t see how we could get rid of all regulations and not expect people to just do whatever is cheapest, despite its effect on the planet.
I would almost think that knowingly damaging the earth would not qualify as doing no harm.
I identify as libertarian myself, although I'm sure most of them would disagree with me on that.
My answer is: as little government as is necessary. But no less than is needed. If fascism is necessary, then Fascism is the right size of government. If anarchy is allowed, then anarchy.