You can live off-grid if you are an able-bodied single between 20 and 40 years old with robust health and you don't care for anything else in the world. You would have to endure harsh conditions and lots of physical labour, you get little in return if at all, but it is physically possible.

However, this changes if you introduce other people to the equation. The issue isn't food, or even drinking water, it is things like heating, electricity, modern medicine, and sewage treatment. Children, pregnant women, elderly, sick, and disabled people require these things to boost their chance of survival. If you don't want an infant mortality rate of 0.85 in your homestead, you better allow young mothers visit a proper hospital. The issue is, at that point what you're doing is basically an amusement park attraction, a bubble of primitive society entirely embedded within the safety and stability of the modern world.

Worse still, building a society that largely made up of homestead communities is an AnPrim pipedream. It is the kind of shit to which you see civilisation regress in movies about a zombie apocalypse. The correct Marxist way to reach our ecological goals is to organise and develop a realistic plan to take control of society on top of its modern infrastructure.