Washington Post has both a targeted and frictionless newsletter sign up button (scroll down to mid article for this actual link).  This example is in a sport’s related article and is for a sports newsletter.  It is super simple, you click on it and just add your email right there.   Not sure I’ll check on it but could you do the same thing with join a FB group or like a specific FB Page (click like here to have similar) stories in your FB Feed.

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