UPDATE 1/12/21: PlayStation has now officially confirmed the below leaked selection of PS Plus games for December: Godfall (its “Challenger Edition”) for PS5, as well as Lego DC Super Villains and Mortal Shell for PS4.
What is Godfall’s Challenger Edition? PlayStation’s blog seems to describe it as a kind of trial version featuring three endgame modes – Lightbringer, Dreamstones, and the Ascended Tower of Trials – for which you’ll be “immediately equipped with a spread of deadly weapons and skill points, letting you team up with up to two other players in co-op”.