collapse of the old society

If you already have reverse osmosis, you're probably good.

As a long cost option for others reading this, apparently the activated charcoal Berkey filters remove 100% of PFAS, and due to the filters being rated to last 8 years of continuous use, are exceptionally affordable.

To bring the costs even lower, you can just buy the filters and not the expensive stainless steel containers by drilling some holes in a 5gal plastic bucket for the filters (it's gravity fed) and place another bucket below to collect it.